Click on "Connect"  and accept to link your wallet

Go to MetaMask.io and select  Chrome for desktop. You can also go directly to the Chrome store, Google Play store, or Apple App Store (soon).  

Switch the connected blockchain by clicking on the tab saying Main Ethereum Network, we need to add the Matic network.Scroll down until you find Add Network :

Metamask_AddNetwork

 

Enter in the Matic Mainnet settings as follows:

Polygon_network_metamask