Halo: The Master Chief Collection XBOX One / Xbox Series X|S CD Key

Select the Start button, then select Xbox.
Sign in. If you don’t have a Microsoft account, sign up. If you’ve ever installed games from the Windows Store, use the same Microsoft account here.
Select My games. Games you have on that device will appear there.
Click on Find games in the Store.
Select Redeem code option and enter your xxxxx-xxxxx-xxxxx-xxxxx-xxxxx key.