Activating an Xbox gift card is fairly easy. Follow these steps:
1) Visit Xbox.com and sign in with your Microsoft account.
2) Click on your profile picture on the top right corner of your screen and select “Redeem Code”.
3) Click “Xbox Gift Card” from the drop-down menu. Input your Xbox gift card code and then click “next”
4) Confirm that you input your Xbox gift card code correctly and proceed.