Go to your Metamask and you simply add the Polygon network to your wallet so you can access it. To do that, you will open the side panel of our MetaMask wallet and click the “Expand view” option under the three dots on the top-right.
Your wallet will open up on a new browser tab like this.
Simply head over to the network dropdown next to the circular logo and select “Add Network”.
You will be redirected to a new screen where you will be able to add a custom network.
You can also access this screen by heading over to the circular logo, accessing “Settings” and then heading over to “Networks” in the left pane.
Now fill out the details.
Enter in the Matic Mainnet settings as follows:
Network Name: Polygon
New RPC URL: https://polygon-rpc.com or
https://rpc-mainnet.matic.network or
https://rpc-mainnet.maticvigil.com or
https://rpc-mainnet.matic.quiknode.pro
ChainID: 137
Symbol: MATIC
Block Explorer URL: https://polygonscan.com/
Once you’ve added all the requested information, you can go ahead and click “Save” and the network will be added to your wallet.
You will be redirected to this screen once the Matic network has been added.
SOURCE: https://coinmarketcap.com/alexandria/article/connect-metamask-to-polygon-network