Please follow these instructions to activate a new retail purchase on Steam:
- Launch the Steam client software and log into your Steam account.
- Click the Games Menu.
- Choose Activate a Product on Steam...
- Follow the onscreen instructions to complete the process.
Log in to the Steam client application (if you haven’t yet, you can download the Steam client here . Click the button labeled "+ Add a Game" on the bottom left on the Steam client and select "Activate a Product on Steam..." and follow the on-screen instructions.
Please see the Retail CD Keys article for more info on registering keys.
Important:
Ensure that you are activating your game through the Steam application. The Steam website cannot be used to activate a game. If you have not yet done so, you can download and install the Steam application by clicking on the green "Install Steam Now" button here: