From the Microsoft Store:

To claim the game, open a Windows 10 or 11 device and search for "Microsoft Store".
Ensure that you are signed into the Microsoft Store under the account you wish to play Wolfenstein II: The New Colossus Digital Deluxe Edition, then select the Account button in the upper-right corner, next to the search bar.
A menu will open with the option to "Redeem code or gift cards".
Select that option, input the 25-character code, and click "Next" to link the content to the account.
From a Microsoft account:

Follow the link here.
Select "Redeem Code".
Enter the 25-character code, select "Next", and then follow the prompts.