To redeem codes on iOS devices, we have created a website connected to the server, where all players can redeem their promotional codes:
https://account.horusheresylegions.com/
Please login on this page with the same email and password you have used to register your account. After you redeem the code, please restart the game to see the new items in your account.
If you run into any problems during the process please leave a support ticket.