Nu Earth: a poisoned planet where endless war rages between the Norts and the Southers. A futile struggle on a hostile planet with no end in sight. But there are tales of a lone warrior. A man who knows no allegiance, the Rogue Trooper!
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