Couldn’t find how to sign on when I bought new 11 ProMax
My local Apple store said I was eligible but I never saw how to get onto the free Apple TV.
iPhone 11 Pro Max, iOS 13
The year offer is for users that bought a new iPhone, iPad, iPod touch, Apple TV, or Mac,
and redeem that offer within 3 months on the new Apple device.
Apple TV+ - One Year Offer - Apple
If you qualify, and if you did as described in the guide, and you still do not get to see the year offer, then contact Apple Support. They can assist in getting you the service, if needed using activation codes.