Operation Valkyrie is a famous plan of the German Resistance to overthrow the tyrannical Nazi government. Standartenfuhrer Gerhard Mayer, a patriot who works in Reich Security Head Office learns that Gestapo has tracked down the conspirators.
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