XCOM: Enemy Unknown - Slingshot Content Pack

The purchased product key must be activated in Steam:

• 1) Go to https://store.steampowered.com/ and click on the green button that says "Install Steam".
• 2) Install and run the Steam client and log in with your existing account or create a new one.
• 3) Click "Add Game" at the bottom left corner of the screen and then select "Activate a Product on Steam"
• 4) The "Product Activation" window will pop up. Follow the onscreen instructions and enter your purchased code.
• 5) Once the activation is complete, you can find the new game in your "Library" tab.
• 6) Press the blue "Install" button to install the game.

Detailed instructions complete with pictures can be found here: instructions-for-applying-electronic-licences-games#steam

If you have any problems redeeming your prepaid code, please contact Steam Support: help.steampowered.com/en