The DLC for this title actually unlocks from the in-game Main Menu. 
 Please follow these instructions:

1)  Boot up Kingdoms of Amalur: Reckoning on your PC.
2)  In the main menu, choose ‘Downloadable Content’.
3)  In the extras menu, choose ‘Redeem Code’.
4)  Enter your code, using your keyboard.  After you enter the code, a pop-up confirms your unlock.
5)  The items are now accessible in the special deliveries chest in Gorhart.

 If you run into further difficulties our support team is always willing to assist you or direct you toward those who can!