Victor Frankenstein, an old friend and a brilliant scientist has managed to resurrect the dead! However the border between life and death is fragile and Victor has learned the hard way that this balance should not be tempered with...
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