How to Buy an NFT on OpenSea Using Polygon wETH

Brittany Salas
6 min readJun 29, 2022


A complete beginners guide to collecting your very first NFT from the Sādu collection backed by living trees!

1. Purchase Ether (ETH). The easiest way to do this is to create an account with a well known exchange of your choice, like Kraken or Coinbase.

Most exchanges require verification or KYC process so it can take up to a week to have your account set up. The next step is to deposit your local currency into your account and exchange it for Ether (ETH). Once again, this could take a few days depending on your local bank.

Alternatively, there is the option to purchase ETH using your credit or debit card within the Metamask wallet extension, but this tends to be more costly and doesn’t save much time.

2. Set up your wallet. Metamask is commonly used and works well with other Ethereum apps. Download the Metamask extension on your web browser.

The extension works well with Chrome so for the sake of these instructions we will assume you are using the Chrome browser. For convenience, pin the Metamask icon to your “Extensions.”

Important note, sharing your seed phrase (the random set of words displayed when you first set up your account) or private key (the secret recovery phrase) will give anyone access to this wallet.

Additional note, the Metamask mobile app is convenient but complicated when it comes to converting ETH to Polygon wrapped ether (wETH) . For those who already have ETH in Metamask mobile, you will not be able to bridge and buy the NFT on OpenSea, even if you add the Polygon network to the mobile app.

From here on out the next steps should only take a minute or two.

3. Send ETH from the exchange described in Step 1 to your Metamask wallet.

Simply copy paste your wallet address to the exchange. Your public wallet address always displays the Copy icon, making it easy to share. Always double check that the wallet address is correct because there is no way to reverse a transfer.

4. To buy an NFT backed by a living tree visit OpenSea, Sādu Summer by Stacie Ant and connect your wallet to OpenSea.

  • Choose the wallet icon at the top right hand corner of the window.
  • Select Metamask.
  • Enter your password. Choose the account with enough ETH to cover the cost of the NFT. Add approximately 20 USD to generously cover transaction fees or ‘gas’. Then click “Next”.
  • Then click “Connect.”
  • Your window will then bring up a privacy policy. Read it then select “Accept and Sign.” There will be no charge for this.
  • Metamask will bring up a different window asking for a signature request. Scroll to the bottom of the Message and select “Sign.” There will be no charge for this.
  • The OpenSea window in your web browser will display your wallet balance.

5. In order to buy an NFT on OpenSea using Polygon you must bridge your ETH to Polygon. Bridged ETH is represented as wETH. From the OpenSea website, click the wallet icon then select the three dots next to your ETH balance and choose “Bridge to Polygon.”

  • Enter an amount that is at least the price of the NFT. The remainder of the ETH tokens in your wallet will be used to cover gas.

Keep in mind there will be a gas fee every time this action is performed. You might want to convert a much larger amount in order to avoid paying gas the next time you buy an NFT on Polygon.

  • In a separate window Metamask will prompt you to confirm the transaction. This will not charge your account.
  • Select “Confirm.”

If you select reject you will see a tile at the bottom of your screen in reference to the failed transaction.

  • In the OpenSea window a pop-up will display while the transaction is being confirmed. Once complete you will be notified with a similar pop-up saying “Transaction Complete.”

6. Now, fear not.

If you select the Metamask extension from the Chome browser it will show your new balance. This balance does not contain wETH. There will also be a transaction entitled “Deposit Ether For” which is a record of your last transaction.

If you select the wallet icon in OpenSea, the wETH will not be displayed. Instead you will see the remaining ETH balance from the last transaction.

7. To see wETH in your wallet you must add the Polygon network to Metamask.

  • To do this select the Metamask icon in your Chrome browser.
  • Select the down arrow next to Ethereum Mainnet.
  • Select “Add Network.”
  • A new tab will open prompting you to fill in a form. The information to fill in the form can be found in the Polygon documentation here.
  • Enter the information into the Metamask tab and select “Save.”
  • In the same tab you will see your new balance of MATIC.
  • Go back to the OpenSea window and select the wallet icon. Your new balance of wETH will be displayed.

7. SUCCESS! You now can easily buy an NFT backed by living trees.

  • Visit the collection, choose your favorite Humanoid and select “Buy Now.”
  • You will be prompted to review the transaction.
  • Once the box is checked you will be directed to “Complete checkout.” Select “Confirm Checkout” and proceed to keep trees alive with your cool new avatar :)

About the Sādu NFT Collection

Every piece contains the unique geo coordinates of a tree. This limited collection is a proof of concept bridging physical trees to digital artwork and capital raise for an all female founding team. The Summer Collection contains 250 of 1000 pieces created by Stacie Ant using generative design(AI). Unmatched in her style, Stacie brings awareness to the emotional dichotomy between self-preservation, technological advancement, and an innate longing to preserve the natural world. Look up the geo coordinates in the Ecosystem Partner Property to verify the tree’s timestamp.

Funding from each sale will be allocated to the artist (25%), ecosystem partners (25%), and Sādu (50%). Sādu will use the proceeds to develop the mobile DApp and P2E tokens. Ecosystem partners, include SeaTrees, The Haiti Tree Project, and Re-Climate 🇺🇦. Additionally, ecosystem partners receive royalties on secondary sales to maintain kelp forests, restore terrestrial forests, and teach regenerative agroforestry.

Download the Sādu app for iOS and Android
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Visit our website.



Brittany Salas

Founder, NyxCarbon. Streamlining sustainability-linked lending. Previously #ClimatePolicy #VC.