Halo: Spartan Assault brings the excitement of Halo combat to Steam for the very first time. Battle your way through 30 action-packed missions against the Covenant as you explore the origin of the Spartan Ops program featured in Halo 4. Earn Steam achievements, complete missions and compete against your friends for the top scores in the leaderboards. It's time to join the assault, Spartan! Features Epic campaign featuring 30 action packed levels with a brand new Halo story set just before the events of Halo 4. Command many of your favorite Halo weapons, vehicles, and armor abilities, and customize your Spartan to create the perfect Spartan warrior. Complete weekly challenges for XP and compete against your friends in Leaderboards for ultimate bragging rights Game supports keyboard/mouse, USB Xbox controller and virtual joysticks for touch.

Go to https://www.xbox.com Login to your account Hover over your account link (the top right of the screen) a menu will appear, click on the "Redeem Code" button. On the next page, click "Redeem" Enter your code Click "Confirm" Click "Confirm" again to assign the key to your account.