1. Go to http://store.steampowered.com/ and download the STEAM client.

2. Click "Install Steam Now"

 
3. Launch Steam and login to your account (create one if you havn't already).
 
4. Then go to 'Games' and click 'Activate a Product on Steam'.

5. Enter the key that we sent you in the email. 

5. Congratulations the game has now been added to your account and can be installed/launched from your games library. 

 If you're still struggling to find where to redeem the key please watch the following video.