Go to Halowaypoint.com/redeem
Sign into your Halo Waypoint account (this is the same as your Microsoft account that you use to login to Xbox Live). If you do not have one, you can create one for free.
Enter the 20-character code, then follow the prompts. Don’t worry about hyphens, the system takes care of those for you.
Confirmation – You’ll see confirmation that your item was successfully redeemed. Items will be saved to your library and will be available when Halo Infinite is released. Once redeemed, content will not expire.