Kodi is a free open-source media player that works on many devices. Follow these steps to install in on your Amazon Fire TV.
Credits: Tom's Guide
1. Go to Settings
In the Settings menu, click Device.
2. Click on Developer Options.
It should be the second option on the list.
3. Enable Apps from Unknown Sources.
If this setting is off, click it once to turn it on.
WARNING: Allowing installation of third-party apps can be a significant security risk. Kodi itself has been compromised in the past. Be aware that installing Kodi on your Amazon Fire TV does involve a certain amount of risk.
4. Acquire the Downloader app.
There are multiple ways to install Kodi, but the simplest way is with the free Downloader app. You can find it in the Amazon Appstore.
5. Direct Downloader to the Kodi website.
The best URL to use is http://www.kodi.tv/download, but you can use other sources, if you prefer.
6. Select the Android app.
The Fire TV’s operating system is an Android branch, so the Kodi Android app will work just fine.
7. Choose the 32-bit installation.
This version of the app generally works best with Fire TV devices, but you can try others if you want to experiment.
8. Click Install.
You can also use this screen to review Kodi’s permissions.
9. Customize Kodi to your liking.
You can access Kodi just as you would any other app on the Fire TV. From here, you can share your media libraries, install add-ons and otherwise tweak Kodi to fit your taste. Bear in mind that if you’re using a Fire TV Stick, you’ll probably have to use a remote media server, whereas the Fire TV has a port for USB storage.