The Apple TV+ subscription gives you full access to the Apple TV+ catalog, but not the other content that can also be accessed through this app.
With the Apple TV app on your smart TV or third party streaming device, you can access:
Unfortunately, currently the Apple TV app on Fire TV doesn’t support in-app financial transactions, to buy, rent, or subscribe for additional content. Instead it will show the How to Watch blurb. To access these other sources, you would need to make the financial transaction on a different, supported device (e.g. iPhone). After that part is done, it would then become accessible in the Apple TV app on Fire TV as well, through the matching Apple ID account.
Extra information for the Apple TV app on Fire TV, Android TV, and Google TV platforms - Apple Support
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