Strategy & Tactics: Wargame Collection is a set of three historical turn-based strategies, in which you are going to take command of the armies in the greatest Medieval wars as well as take control of countries and nations during World War II.
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