Connections on the web and several other devices are currently being worked on. You can get the new VidAngel app on iOS and Android mobile devices. Using the updated app will allow you to cast to your Fire TV. The best part is, you can hard close the app on your phone to use for surfing the web, cruising Facebook, or making calls; AND you can use the Fire TV remote to control the movie once it starts.
Here's how to get started:
First, you'll need the VidAngel app on your iPhone or Android mobile device. Make sure that it's update to the most current version.
Now get your Fire TV ready and turned on. Check that your phone is on the same WiFi network as your Fire TV.
Either browse or search for the movie/show you would like to watch. When you found something you would like to watch, set your filters and then tap on the Watch With Amazon (or Netflix) button.
The movie/show will then verify the title.
Once the movie/show is done verifying, you are ready to watch. Tap on the Watch On TV button. This will open the casting tab to allow you to pick your Fire TV to cast too.
You will notice that if a device is online it will show in the device icon.
Tap on the Fire TV and once connected it will start on your TV. From the app you will be able to control the movie, or, you can shut off your phone and use the default remote for your device to control the movie.
If you want to disconnect from the movie you can easily do this by tapping on Disconnect.