metamask can only access via desktop browser you can download on chrome store or mozilla add-ons. You can import your wallet you use on smartphone or you can create a new one, its same for another wallet when you create a new wallet you should make a pasword and save the parphrase backup if your browser got an error or your reinstall your pc. This very important if you dont want lose your asset. Metamask have a high security level like another wallet. Another person can't easy to hacking your wallet because only you can access it.
If you not found your token while you open metamask you can add manually the token you have by manually input contract address , ticker and decimal and your token will show on your balance