I got free Apple TV when I purchased my iPhone why isn’t my smart tv app applicable

With the Apple TV app on your smart TV, you can access:

• iTunes Store movies and TV shows (buy or rent);
• Apple TV+ channel featuring Apple Originals, by subscription;
• other premium Apple TV app Channels, each by subscription.

The year offer subscription is for Apple TV+, not for the other services. Apple TV+ content will not ask additional payment from subscribers.

Not all models are supported . Ones that are require a software update, then you install the TV App.

More will be added soon. I don’t know when .

Devices you can use with the Apple TV app and Apple TV+

https://support.apple.com/en-ca/HT210740

All the ways to watch Apple TV+ - Apple Support

https://support.apple.com/en-ca/guide/tvplus/welcome/web

Also to correct you, you received free Apple TV Plus which is accessed through the Apple TV. App.

tv+ is Apple Original content