Someone please tell me how to do it, cuz idk.
go to your own profile, click on your service record for halo 5, and click on the requisitions tab in the blue text at the top
hope that helps!
Follow this link. you cant buy the bundles here though: https://www.halowaypoint.com/en-us/games/halo-5-guardians/xbox-one/requisitions/store
if you want the bundles, buy em on xbox.com (https://store.xbox.com/en-GB/Xbox-One/dlc/Halo-5-Guardians/9a924f64-6ac5-4380-b249-8162269c15cc) and then come back to this page to open them - https://www.halowaypoint.com/en-us/games/halo-5-guardians/xbox-one/requisitions/unopened-packs