Enligt instruktionerna är det ingen förmån. Du ska teckna via appletv-appen.
To sign up, you'll need to head to the official Apple TV app on your Xbox (search for it on the Microsoft Store by pressing the "Y" button and typing "Apple TV"). When it starts up, you should see the free trial offer on the front page - if you don't, it's probably because it's not applicable in your region unfortunately.
From here, the steps should look something like this:
Hit the 3-Month Free Trial button
Use the QR code to create or sign into your account on another device
Accept the offer for 3 free months by hitting "Subscribe"
Return to the app to begin watching your content