http://www.mmobomb.com/giveaway/dirty-bomb-steam-codes
How to get and use your Key:
1. Log in to your MMOBomb account to get your key. If you don’t have one, register for free HERE.
2. Click on the big yelow button at the top. Copy and paste your key to a safe place as you may not be able to retrieve it once closing your browser.
3. Launch the Steam client software and log into your Steam account.
4. Click the Games Menu.
5. Choose Activate a Product on Steam.
6. Follow the onscreen instructions to complete the process.
7. Make sure you never miss a giveaway, follow our updates via Facebook, Twitter!
8. Enjoy the game! Have Fun!