You enter the code into your own Steam account. It's yours forever.
: Once a key is acquired, users must enter it into the "Activate a Product on Steam" menu. If successful, the game is permanently added to the user's library and can be re-downloaded at any time. System Requirements for PC Efootball Pes 2021 Activation Key Pc
Redeem it immediately in Steam (Games > Activate a Product on Steam). Do not share the code online. You enter the code into your own Steam account