To access the game, open your Windows 10 or 11 device and search for "Microsoft Store"
Make sure you're signed into the Microsoft Store with the account you want to play Fallout 76 with, then click the "Account" button in the top right corner, next to the search bar.
A menu will open with the option to "Redeem a code or gift card."
Select that option, enter the 25-character code, and click Next to link the content to your account.

If you're from China or Russia, use a VPN if you can't get the game.
Or change your PC region to the US