In order to sell your Pop Shots on OpenSea, you will need to hold MATIC tokens. These tokens can be added through Pop Shots for $1 (optional, but recommended) at the time of your Pop Shots purchase.
To connect your MATIC tokens to Metamask, you will need to configure Matic’s
Mainnet URL on Metamask.
1) To add Matic’s Mainnet, click on the Network selection dropdown and then click on Custom RPC.
2) It will open up a form with 2 tabs on the top, Settings and Info. In the Settings tab you can add
Matic Mainnet in the Network Name field, URL
https://rpc-mainnet.maticvigil.com/ in the New RPC URL field,
137 in Chain ID field,
MATIC in Currency Symbol field and
https://polygonscan.com/ in Block Explorer URL field.
3) Once you’ve added the information click on Save. You will be directly switched to Matic’s Mainnet now in the network dropdown list. You can now close the dialog.
For questions regarding adding MATIC to Metamask, you will need to reach out to Matic support directly.