The app has autoupdate feature so you will no longer need to sideload apk. The app checks if the new version is available once per day. Also you can manually check the new version in Settings -> About. ;)
Install TiviMate app on Fire TV device by sideloading apk from this link:
https://www.mediafire.com/file/6f914mx41jaf9m0/tivimate_4001.apk/file
. Launch TiviMate and go to Unlock screen
Log in to your TiviMate account
Activate the device