1. Launch the Steam client software and log into your Steam account.
2. Click the Games Menu along the top of the Steam client.
3. Choose Activate a Product on Steam.
4. Follow the onscreen instructions to complete the process.
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: