Heaven’s Above takes the player out of the first-person perspective and presents itself as a top-down shooter. Heaven’s Above lets you play 5 maps from the campaign in single player or co-op mode including one of the monumental boss fights.
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