If you already have an account with Steam and have the application installed on your computer, skip to step 2.

1. Download and install the Steam client.
2. Run the Steam client software.
3. If you are a new Steam user, click the “Create a new account” button to register a new account.
4. If you’re an existing Steam user, log in.
5. In the bottom left hand corner of the client is a
   "+ Add a game..." button. Click it.
6. Select "Activate a product on Steam".
7. Follow the on-screen instructions and paste in the product activation key when asked.
8. After a couple of minutes Steam will authenticate the code.
9. Click on "Library". You should see you game there.
10. Click on your game to start downloading it.