📚Buyer's Detailed Guide

A Detailed Guide for buyers, for both beginners and those curious about specific steps.


  • Who is this guide for? This detailed guide is best for beginning crypto users (if you have never used Metamask before), or if you're stuck on a section in the Quickstart. We recommend many users start with the Quickstart instead. Notes intended especially for beginners are sometimes marked with 🔰, notes meant for those with strong technical background looking for completeness are marked with 🧑‍🔬.

  • Why are there some duplicates with the Quickstart? Some title sections are duplicated with the Quickstart, as one of the goals of this guide is to help those stuck on the Quickstart. The duplicated sections are mostly in the second half of this Detailed Guide, and words in italics are new content in this section.

  • How is this Detailed Guide Organized?

    • This detailed guide starts with a few Prep Steps, steps that relate to setting up crypto in general, and not steps unique to using our site. You may already know some of these, in which case you should read the summary and skip the videos.

    • Then it presents our 20-minute Walkthrough Video on using our site. Much of the video is explained in in two sections:

    • An Appendix follows that discusses using alternative platforms. This guide importantly presumes you are using a desktop or laptop with the Metamask web3 wallet. This guide less importantly presumes you're using Coinbase, Chrome, on a Windows 10 or 11 setup. Thus, the Appendix discusses alternate platforms.

🔰Prep 1: Intro to Crypto

Never worked with crypto before? No worries, we have some links for you to get acquainted with cryptocurrencies.


  • Money has evolved from being commodity-backed to being digital, with centralized authorities like banks controlling it.

  • Decentralized digital currencies like Bitcoin solved the "double spend" problem, laying the groundwork for blockchain technologies.

  • Blockchain networks operate transparently and securely without the need for central oversight, enabling peer-to-peer transactions.

  • Smart contracts extend the capabilities of blockchain, allowing for programmable, automated transactions.

  • WaterMelonMarkets leverages these blockchain and smart contract technologies to offer a decentralized marketplace for gift cards.

🔰Prep 2: Buying Your Crypto

The way most people buy crypto for their first time is through Coinbase. It's a large, trusted, multinational company that lets you exchange regular money (credit card payment, bank payment) for Crypto like Bitcoin, Ethereum, and MATIC (we only need MATIC for WaterMelonMarkets).


  • The video demonstrates how to purchase cryptocurrency on Coinbase, offering multiple payment methods like credit cards and bank deposits.

  • Using a credit card incurs higher fees (at time of video, 4.5% total), while depositing money from a bank account to your Coinbase balance lowers the fee to 1.49%.

  • After depositing, go to the Buy/Sell tab, select your account balance as the payment method, preview the transaction for fees, and confirm the purchase.

  • For the purposes of understanding WaterMelonMarkets, you don't need to follow the videos endorsements of Revolut, or recurring buys, unless you want to proactively invest in crypto.

  • The video mostly covers Bitcoin, but the actual coin you need to buy is called MATIC-Polygon (video link to how to use Coinbase for MATIC-Polygon).


  • Binance is another popular exchange. You can search Youtube for tutorials; here is just one video.

  • You can ask a friend for crypto, although they need to know to send you MATIC on the Polygon chain.

  • 🧑‍🔬Technical (for experts only):

    • There are other methods, like using ETH on the Ethereum chain and the Polygon bridge to convert that ETH to wETH on Polygon. And then using Matcha.xyz to convert.

    • Likewise, you can use Bitcoin bridges to go from Bitcoin to Ethereum's network, and then Matcha to convert to the bridged BTC to ETH. And then use Polygon bridge like above. This is likely overkill though.

Extra Notes for Beginners:

  • Coinbase is a large company and their support documentation and support is very comprehensive. They should be able to directly help you do the transfer above.

  • Another option is asking a trusted friend to help you buy MATIC. Ideally this friend has used Metamask before, and even better if they know how to switch to Polygon on Metamask.

Prep 3: Setting Up Your Smart Wallet

Video: How to Set up Metamask

  • Guy's tutorial introduces MetaMask, a cryptocurrency wallet extension for web browsers, which allows secure interactions with decentralized apps on blockchains like Ethereum without revealing your private keys.

  • To get started, download the MetaMask extension from metamask.io, set up a new wallet, and ensure your seed phrase is safely stored.

  • Once the wallet is set up, you can add Ethereum (ETH) by purchasing directly within MetaMask or transferring it from an exchange.

  • The video covers key features such as how to use MetaMask's own swap service to trade tokens, and how to customize gas fees in advanced settings to manage transaction costs efficiently.

Note: The tutorial also discusses using Binance Smart Chain, but for the purpose of this summary and your focus, users are advised to concentrate solely on the MetaMask setup for Ethereum. You'll need to switch from the Ethereum chain to Polygon in a video below.

Prep 4: Switching to the Polygon Chain on Your Wallet

Video: Switching to the Polygon Chain.

Beginner Note: Polygon is both the name of a chain (i.e. an alternative to Ethereum), sometimes informally used to refer to the native token on the chain, MATIC. This section only covers switching to the Polygon chain. It doesn't cover running transactions or buying MATIC tokens on the chain (which you might have done already above, or can do using the instructions below).


  • The video starts by discussing how MetaMask, traditionally used for Ethereum, can also be connected to other networks like Polygon for cheaper and faster transactions in decentralized applications.

  • To add the Polygon network, users need to open their existing MetaMask wallet and click on the circle icon (usually displaying their profile picture or a generic image) located at the top right corner.

  • After clicking the circle icon, users should navigate to 'Settings,' then choose 'Networks' from the left-hand menu. They can then select 'Add Network' to manually input Polygon's network details.

  • Users are urged to make sure they have backup access to their MetaMask private keys or seed phrases before making any changes, as a safety measure.

  • You may skip the section about Bridges if you are a beginner. Bridges are complex, sometimes costly, and rarely worth it if you are new to crypto.

  • Completing this setup allows users to enjoy decentralized apps on the Polygon network with reduced transaction fees and faster block times compared to Ethereum.

Note: This summary focuses on the steps for setting up MetaMask with the Polygon network. Make sure to be cautious of the details and transaction fees involved.

Full Video Walkthrough (Overlaps with Sections I and II)

At this point, if you are a beginner, you probably want to view the full-length walkthrough video carefully. This video overlaps with Section I and Section II below.

Section I: Start and acquire USDC-Polygon and MATIC

Step 1: Buy MATIC Tokens on an Exchange (e.g. Coinbase)

This section is derived from the Quickstart guide. However, we add detailed notes in italics.

  • 1A: Go to a Centralized Exchange like Coinbase.com

    • 🔰This is somewhat covered already by the previous section in "Prep 2" -- if you are having trouble with this section, review the above section and video, and search Youtube videos for "walkthrough buy crypto / MATIC on Coinbase". For USA users and other countries where Coinbase is dominant, Coinbase is a good exchange to start with. Coinbase is >$10bln exchange and so has extensive email, phone, and online / Youtube support. Alternatives include Binance.

    • Technical note: An "exchange" is just any location where you can trade your normal cash (like USD, GBP, INR, CNY, etc) into

  • 1B: Search for MATIC on Polygon, sometimes just called "Polygon"

    • You can use the search bar of your exchange to buy MATIC. Usually you don't need to specify a chain, but if there are multiple MATIC or Polygon options, choose the one that is most popular and looks closest to "MATIC-Polygon".

    • 🔰 We chose Polygon as the chain for our transaction because most transactions are on the order of 1 cent (0.01 USD); this contrasts with up to $10 for some complex Ethereum transactions. MATIC is the native token of the Polygon chain. Native token means that MATIC is the token used to pay for transaction "gas" by default on Polygon. Conversely if you have no MATIC in your address, you can't run any transactions. Thus, it is both the default token we recommend in getting value in and out of the Polygon chain, and you should always leave about $1 worth of MATIC in your wallet (don't sell it all) so you can continue to run transactions.

  • 1C: If you have an option, ensure it says "Polygon" and not "Ethereum" (ignore if no option exists for you)

    • For some time in 2022, Coinbase would default to sending you MATIC token on the Ethereum chain, which makes no functional sense. A workaround during that time period was to transfer MATIC to you Coinbase Wallet, ensuring it says "Polygon" for the chain. These days, Coinbase directly lets you transfer MATIC on the Polygon chain. If you're not experiencing the above issue, you may ignore this comment.

  • 1D: Buy an amount of MATIC whose dollar value is about $2 more than the Selling Price item you are buying. For example, if you are buying a $50 Face-Value gift card with Selling Price of $30, buy $32 worth of MATIC.

    • You should buy $2 more than you need as a buffer. First, you will need at least $0.10 in MATC to pay for gas, though I would keep >$0.50 in MATIC to be safe. Second, you may pay a small fraction, like 0.001, in converting your MATIC to USDC-Polygon in the future

Figure 1.1: How to buy MATIC on Coinbase.com

Video 1.1 Click Here to watch a video of the above

Step 2: Transfer MATIC to your Web3 Wallet (e.g. Metamask) Using Polygon

  • 2A: Hit "Send and Receive" and then put the amount you just bought ($5 in the below example) in the dialogue.

    • These specific instructions are only valid for Coinbase on Chrome / Desktop. If you are using alternatives, see the alternatives section at the end.

  • 2B: Ensure the "Asset" line says "MATIC" or "Polygon". IMPORTANT: Ensure the "Network" says Polygon and not Ethereum.

    • For a period in 2022, Coinbase would send MATIC-token by default on the Ethereum-chain. While you can trade MATIC-token on Ethereum-chain, this makes little sense as most people transferring MATIC want it to be transferred on Polygon-chain, as it's the native token there. If you believe you've sent the MATIC tokens, but can't find them, ask the sending exchange to give you the exact transaction ID, and you can usually find it on www.polygonscan.com or etherscan.com or Google.

  • 2C: Double check to "To" line has your exact Metamask address. Then hit "Send Now".

    • 🔰Beginner note: In order to find your address, you can follow Step 3) below

  • Click Here for a video link.

Step 3: Ensure your Web3 Wallet (e.g. Metamask) Receives Your MATIC

  • Fig 1: Steps 3A-C below:

  • 3A) Open up Metamask (fox icon), usually an icon in the top right of your Browser (Chrome)

    • Technical Note: Metamask is a Chrome extension, which means that it works along with your browser, Chrome, to allow your browser to access different aspects of your wallet. The Metamask window itself is the best place to find current balances, recent transactions, and confirmations for all the technical details of your web3 wallet. Chrome's browser window is the best place to interact with the web3 app itself, whether the app is an exchange, or for us, WaterMelonMarkets.

  • 3B) Choose the right account that you sent MATIC to.

    • 🧑‍🔬: Metamask generally allows you to have one secret Seed Phrase. This secret seed phrase is used to generate all your Addresses (synonym here for "Accounts") tied to this phrase. Some users will just use one address, while most users use anywhere from a few to a few hundred addresses. The red circle above around "F Acct 1" shows the currently selected Address. Each Address can be thought of as a segregated bank account, like if you had a few separate accounts at a bank. In order for Address 3 to run say, a $50 USDC-Polygon transaction, Address 3 needs to have $50 USDC-Polygon and some MATIC. It is not enough for Address 2 to have these funds. You may transfer funds between your Addresses to run transactions. While each Address is segregated technically, Addresses tied to the same seed phrase do have some "group properties". Namely, anyone with the seed phrase can a) prove that all the Addresses belong to the same person b) have full master control over all Addresses. Of course, best practices dictate that you keep your seed phrase backed up and private, as anyone who knows it will have full access to your accounts.

  • 3C) Select the right chain, which is Polygon. If you don't see Polygon after a minute of trying, we suggest you follow this guide.

  • 3D) Go to Activity, and you should see the exact number of MATIC tokens you sent before:

    • This step is optional, but just helps make sure that all your MATIC has arrived, and you're in the right account.

Step 4: Convert your MATIC to USDC-Polygon

You can do this in a variety of decentralized exchanges (dexs), but in this example we will

  • 4A) Go to Matcha.xyz

    • Note: Matcha.xyz is a decentralized exchange aggregator (finds the cheapest exchange amongst many decentralized exchanges). A decentralized exchange is a web3 application that let you change one token to another, like wrapped Bitcoin to wrapped ETH, or in our case below, MATIC-on-Polygon to USDC-on-Polygon. Some customers prefer using the most popular decentralized exchange directly, which is Uniswap.org

  • 4B) Change your chain to Polygon

    • You did this step before in 3C) above, which has a good guide on how to add and change chains on Metamask.

  • 4C) Put MATIC as the token you're trying to convert. And for target token, choose USDC-Polygon. Convert about 1-2 cents more than the price of the item you're buying. (USDC-Polygon is known on Matcha.XYZ as "USD Coin (PoS)".

    • Ensure that your screen looks something like below. You want the "Pay with" token to be MATIC. If there are lots of "MATIC" variations, choose the top one and ensure it doesn't have extraneous descriptors like "wrapped" or "staked" or "liquid". You want to "You receive" token to be USDC, which should be called "USDC (PoS) on Polygon". Again, choose the top one without extraneous descriptors, not "wrapped" or "aave".

  • 4D) Hit Convert, confirm in Polygon, and you're done!

    • The fee should be relatively small, $0.05 or less.

    • 🔰Beginner Note: If this is your first Metamask transaction, you may follow this walkthrough. When you request the transaction in the Chrome browser, the Metamask pop-up will show up. If you accidentally close this, you can always reopen it by clicking on the "fox" icon in the top right of your Chrome browser. Metamask will show the transaction confirmation: key things to check include that i) this transaction is for the amount you thought it was (around "$5.26" for my transaction below, and ii) that the Gas section is reasonable. You can leave the Gas at "Site Suggested" below, but if you make changes, we strongly recommend you choose "Aggressive" gas or "Market" gas. Do not choose low gas -- Polygon transactions are so cheap that the cent you'll save with low gas won't be worth the chance of a stuck transaction, which requires digging in to debug.

Click here for video.

Congratulations! At this point, the hardest work is done! You've learned about crypto, set up your web3 smart wallet, bought some USDC-Polygon and MATIC-Polygon, and have run an exchange transaction. The most complex part of crypto is done, and you're just a bit away from making your first purchase with WaterMelonMarkets.

Section II: Your First Purchase: Step-by-Step

Step 5. Go to WaterMelonMarkets.com, find a card you like, and click Buy

  • 5A) Go to our site, browse through brands you like, and click on one.

    • Unlike the web3 topics above, our site looks similar to a regular commerce site. Go to the home page www.watermelonmarkets.com to browse brands. Each brand has a set of cards sold by different sellers. The cards have varying discounts (e.g. -5% to -70%) and varying sizes (e.g. from $3 to $1000). You can click into each card to see if there are special notes by the seller (expiration dates, country restrictions). Generally we allow the seller's special note terms to prevail, unless it is outside the range of our acceptance guidelines, or seems deliberately misleading. The remaining sections of Step 5 is standard ecommerce.

  • 5B) Find the card that you like

  • 5C) Hit the Buy button

Step 6. Go through the Checkout Process

  • This part is probably easiest if you just try checking out yourself first, carefully paying attention to each part of the checkout process. Then, when you are stuck on something, come back to this section and read into the details on where you're stuck. Otherwise, this section has a lot of extraneous details for items you might find easy.

  • 6A) Enter your email (to receive notifications and your card)

    • Your email is your primary login for your normal web account at WaterMelonMarkets. A normal web account is needed for many parts of your transaction, like helping you communicate with sellers, having a record of all your purchases, and releasing gift card information to you. To review, WaterMelonMarkets is comprised of A) web3 smart contracts, which is what Metamask helps you interact with, and B) a normal web database that you use your email to log into.

  • 6B) Connect your wallet to the site. Ensure it is Polygon and has the funds you need.

    • Beginner Note: 6B,C,D are nearly identical to Step 4) above, so if stuck here, please review that section.

  • 6C) Increase your USDC allowance. (This is a standard step all site that use tokens require; hitting this does NOT spend your USDC yet). Wait for the IncreaseAllowance transaction to finish

    • This is the first of two transactions you need to run to finish your purchase. This transaction is similar to Step 4D) above. We recommend you run the transaction with either default gas, or aggressive gas. Increasing your token allowance is a standard part of web3 transactions. By convention, the allowance is increased without limit to reduce transaction costs in the future. This is safe because our actual contract is open source and each transaction is totally transparent, so you know exactly what the contract will do. You may revoke permissions anytime in the future.

    • Generally, you'll want to leave your browser open for 1-5 minutes if the loading symbol is still showing. If your transaction does not succeed, please check the transaction on the blockchain using Metamask, and ensure it has been included in the blockchain. If this transaction has been included in the blockchain already, and your browser is still stalled after >5 minutes, you may just try the checkout again. The system should detect you have already approved USDC-Polygon and skip 6C) automatically next time.

  • 6D) Then click Initiate Transfer. Approve and wait for that InitiateTransfer transaction to finish.

    • This is another transaction and similar to 6C) and 4D). Please run the transaction with default or aggressive gas. Keep the window open and wait 1-5 minutes for the transaction to complete. The site should then forward you to a Thank You page where i) for Verified Transactions, you get your card info immediately and ii) for Deposited Transactions, you get a receipt and should expect your card info by the end of the next business day.

    • In case the site does not automatically foward you, please check your Metamask wallet to ensure the transaction completed correctly (raise the gas cost if needed after a minute).

      • If the transaction did not complete on Metamask (give it a minute), it will not complete on our site. Your best bet is to try one more time from the start.

      • If the transaction DID complete on Metamask, our site should give you the Thank You page within 60 seconds. In rare cases where the transaction complete on Metamask but you don't have a Thank You page, you qualify for fast-response VIP support: simply email support@watermelonmarkets.com with Subject: [VIP] and include your transactionID, and we'll manually debug it for you!

Walkthrough video section here (please note that the video does not show Metamask, you'll need to follow the voiceover instead).

Step 7. Await Delivery and Finalize Your Transaction! White-Glove VIP Support Available to Help

  • 7A) For Verified Transactions (most gift cards), you should receive your card immediately within 5 minutes. If the redemption info doesn't show up on your screen, also check i) your email and ii) login to your profile and look at your transactions -- it's usually all there.

  • 7B) For Deposited Transactions, you should wait for the end of the next business day to allow the seller time to manually send it to you. The card should be in your email or after you login.

  • 7C) In the unlikely case the card is late / not as described, you may email support@watermelonmarkets.com for help.

  • 7D) In the more likely case the card works, go to your profile page after you log in to release funds!

Remember! Once you finish your payment and have a transactionID (from Metamask / Polygonscan), you qualify for white-glove VIP support, where we'll manually help you with all issues and complete the exchange. Simply email support@watermelonmarkets.com, write [VIP] in the subject line, and include your transaction ID.

Appendix 1: Alternate Platforms

This guide importantly presumes you are using a desktop or laptop with the Metamask web3 wallet. This guide less importantly presumes you're using Coinbase, Chrome, on a Windows 10 or 11 setup. Thus, this Appendix discusses alternate platforms. We start with platforms that are *least* important, since these are the ones that are perfectly okay to choose alternates for. Then we move onto platform choices that will significantly change your interaction.

  1. Operating System Alternates: In addition to Windows, we have full support for MacOS / OSX / Linux. Our developers / founders use all of the above operating system, and in 2023, the base operating system matters a lot less.

  2. Browser Alternatives: All our development and testing occurs in Chrome, so we strongly recommend that -- it also happens to be the most popular browser by far. We also run substantial tests on Firefox -- a broad, free alternative to Chrome. Browsers are most impacted by how they interact with Metamask, and while other browsers *can* work, if they don't play nice with Metamask, using them may be substantially different from Chrome / Firefox. This includes Safari, Edge, Opera.

  3. Smart Wallet Alternatives: We strongly recommend Metamask, as this is the leading web3 wallet in many situations. The web3 / crypto processes are complex, and other web3 wallets may have totally different interfaces / names for doing tasks. If you must use an alternative, use Coinbase Wallet (the web3 wallet from Coinbase, this is different than the "Coinbase website"). Generally, no other web3 wallet brand are tested; if you use them you're playing in expert mode and on your own out there.

  4. Mobile / Desktop: While our site supports Mobile for browsing, we strongly recommend you use a Desktop (including a Laptop) for the site. Mobile's interactions for web3 wallets and payments are very different, and web3 transactions generally require a lot of care, which is difficult to do in a mobile enviroment.

Summary: Feel free to use your own operating system. For browser, we recommend Chrome but Firefox also works; anything else is at your own risk. For web3 wallet, we strongly recommend Metamask. And please don't use mobile for your actual web3 transaction.

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