Sid Meier's Civilization® V: Brave New World is the second expansion pack for Civilization V - the critically acclaimed 2010 PC Game of the Year. This new expansion provides enhanced depth and replayability through the introduction of international trade and a focus on culture and diplomacy.
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