Sanctum 2 is the sequel to the world’s first Tower Defense/FPS hybrid game. Pick from four unique character classes and embark on a mission to protect the oxygen-producing Cores from hordes of deadly aliens who are threatened by their existence.
Open the Steam client, login and locate the Games tab on the top menu. Click this and then select “Activate a Product on Steam…”
Enter your unique code that's displayed on the 'Orders' page of CDKeys.com and follow the prompts to activate.
Your game is now viewable in the “Library” tab and is available to download/install when you’re ready. You can find additional support for the Steam client here: https://help.steampowered.com/en/wizard/HelpWithSteam