Install Downloader
From the Fire TV Home screen, open Find, search for Downloader, then install and open the official app.
Allow the installation
Go to Settings → My Fire TV → Developer Options → Install unknown apps and switch Downloader on.
Enter the LibertyTV code
In Downloader, enter 4252041 and select Go. You can also enter the direct URL from this guide.
Install and open
When the download finishes, select Install, then open the LibertyTV player.
Sign in
Enter the exact username and password from your LibertyTV welcome email. The custom app does not need a server URL.
Good to know: These APK steps are for compatible Fire OS devices, not Vega OS models such as Fire TV Stick 4K Select. Confirm your exact model with support first. On a supported Fire OS device, if Developer Options is hidden, open Settings → My Fire TV → About and select your device name seven times. Do not bypass a security warning or a blocked installation.