Space Hulk: Ascension is a 3D, digital, turn based, strategy game, which re-interprets the classic board game experience, and adds new RPG style mechanics, new weapons and missions, new enemy types, 3 playable chapters and loads of other new features to the single player experience.
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