Follow these instructions to activate a new retail purchase on Steam:

• Launch the Steam client software and log into your Steam account.
• Open the Games menu.
• Choose Activate a Product on Steam.
• Follow the onscreen instructions to complete the process.
• The game will be downloaded and added to your Steam LIBRARY.

Additional information about Steam:

• Activation will be blocked for 1 hour if you type an incorrect serial number three times in a row.