Prior to early 2020, you could download and install the BritBox app on the Fire TV and have a stand-alone subscription directly through the app. Now, the only way to get BritBox on the Fire TV is to subscribe via a Prime Video Channel. Note that this does require you to have an Amazon Prime membership to subscribe. To get it on your Fire TV stick, follow these instructions:
- Launch the Prime Video App on your Fire TV stick
- Go to the Channels section up top
- Scroll down to Prime Video Channels
- Select BritBox
- Select Add channel (up top)
- Confirm subscription
You are now subscribed to BritBox and the charges will bill to your Amazon account every month.
If you are not a Prime Member, check out Acorn TV which has similar content and can be installed outside of Prime Video.