With Apple One, you subscribe to a bundle of services, including Apple TV+. If you had previously subscribed to Apple TV+, then you will find that Apple One doesn’t include Apple TV+ during the first free trial month, regardless of device. Users should account for one month overlap. Either wait out one month, or re-subscribe for one month. The superfluous subscription would then be canceled automatically when the free trial month is over.
As for accessing Apple TV+ in the Apple TV app on Fire TV:
When signed in with the matching Apple ID account, subscribers should have full access to the Apple TV+ content, but this subscription will not include items from the iTunes Store (buy or rent), nor in-app third party subscription channels. Furthermore, currently the Apple TV app on Fire TV (or Google platforms) doesn’t support (most) in-app purchases processed through Amazon Appstore (or Google Play Store). Instead, you would get the “How to Watch” blurb explaining that, and that users should buy, rent, or subscribe on a different supported device (e.g. iPhone).
To access the Apple TV+ content overview in the Apple TV app, navigate to the Apple TV+ tab in the sidebar.
You could also notice the tv+ logo in the corner of applicable content tiles, to signify inclusion in Apple TV+.
