I bought an iPhone. How do I get my free 3 months of Apple TV

See the information in https://offers.appletvapp.apple/tvp01213mf including the following:

Redeem 3 months free of Apple TV+ now.

You can start your 3 months free subscription to Apple TV+ after setting up your new Apple product. Here's how to redeem your offer:

1- Turn on your new Apple device and sign in with your Apple ID.

2- Open the Apple TV app. Make sure your device is running the latest version of iOS, iPadOS, tvOS, or macOS.

3- The offer should be presented immediately after launching the app. If not, go to the Apple TV+ tab where you'll see the offer.

4- Tap Enjoy 3 Months Free.