How do I activate a game on Steam?
If you follow these steps you should get your game immediately.
1. Open an account with Steam. (please see point above for details on how to do so)
2. Download and install the Steam client. (please see above)
3. Run the Steam client software and log in with your Steam account details.
4. In the bottom left hand corner of the client is a “+ Add a game…” button. Click it.
5. Select “Activate a product on Steam”.
6. Paste in the product activation key you received from GMG.
7. After a couple of minutes Steam will authenticate the code.
8. Click on “Library”. You should see you game in the Library.
9. Click on your game to start downloading it.