On the Fire TV home screen, open Search.
Type "Downloader" and install it.

Go to Settings → My Fire TV → Developer Options.
Can't see it? Open About and click your device name 7 times.
👇 This step is explained in the video below.

In Developer Options, open Install unknown apps.
Turn Downloader ON.
Watch how to do it 👇

https://www.youtube.com/watch?v=gS0nMSNheIY

Open Downloader and type the code : 224877 on the app below.
Press Go, let it download, then press Install.