World War III is over, the world's infested with mutants and your supplies are running out. Fight your way down this damned hotel, from your penthouse on top to the first floor. Craft weapons, search for food and reach the exit. Otherwise you'll be torn apart, starve to death or maybe both...
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