How to enable unknown sources on Fire TV devices
To install apps that are unavailable locally on0 Amazon Fire TV devices like the Fire Stick and Fire Cube we'll first need to enable installing apps via unknown sources. We can do that easily using the steps below.
From the Home screen, long press the Home button on your remote then select Settings.
Scroll all the way to the right and select My Fire TV
Select Developer Options
Turn ON - Apps from Unknown Sources
That's it! You're now ready to sideload apps to your Fire TV device.