Extension:
Visit OpenSea from your browser.
Click on the wallet icon in the top right corner.
For Ethereum or Polygon, select “Phantom”.
For Ethereum and Polygon, select “MetaMask”.
Mobile:
If you are on mobile you will need to visit https://opensea.io in the in-app browser.
You will need to click on the three lines in the top right and select "Connect wallet" before continuing.
Then select Phantom for Ethereum or Polygon.
Note: You will only be prompted with the "Sign Message" screen on the first time visiting OpenSea.
You are now connected to OpenSea and free to make bids, purchase NFTs, or list your NFTs for sale!