This is not for steam, its for the rockstar launcher, if you own gta v, you probably have a rockstar account already
- Go to the giveaway page
- https://socialclub.rockstargames.com/rockstar-games-launcher
- Download the launcher
- Install it
- Login/Register
- Click on Grand Theft Auto: San Andreas
- Click Claim Free Game
- Click Claim Free Game (again)
- Click Redeem Grand Theft Auto: San Andreas
- The game is yours forever
