Metamask is a wallet that you can use to send and receive Ether (ETH) and all ERC-20 tokens. It’s also a way to access services built on the Ethereum network. You can use it as a web browser extension or as a mobile app on your smartphone.
I suggest you to download Google Chrome to start. Then click here and add that to the browser. Now you should see the Metamask icon on the right tab. Click on the orange fox to open the wallet.
So choose a password for your account and ensure that the MainNet network is selected. At this point you are able to send and receive ERC-20 tokens trough your Ether (ETH) public address (that you can easily copy).
If you want that a specific ERC-20 tokens is displayed in the list, you have to add it manually (Add token) and paste the Token address Contract. Remaining fields will be completed automatically.