Apollo4x is a casual-to-difficult space trading tycoon game, where success is measured in earnings from how efficient your trade routes are in transporting supplies to demands on your planets. Combat is card based, and uses a unique system never before seen.
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