1. Make sure you have a Steam account, where you can activate the codes.
2. Now, go to http://goo.gl/wQnyqK/ and register an account.
3. After registering, you might need to confirm your e-mail. Check it!
4. When you're done registering, you can start earning games for free! There are many ways you can earn them:
          - Playing games
          - Watching videos
          - Downloading Android/iOS games/apps
          - Doing tasks
          - Inviting friends
          - Completing achievements
          - Logging in daily
          - Doing surveys, if you wish
          - Paying for coins, if you wish
          - Trading Steam games/trading cards for Coins
          - Trading Steam emoticons for Coins
          - and many others!
I get every day a game for free, trust me. It's easy, fast and legit. Good luck!