Google Cast with preinstalled TV app

I have Chromecast Android TV-box with preinstalled TV app(lets name it FUN TV) from service provider.
I created a group in HA to turn it on/off with Samsung TV, fine it turns on and off but on TV screen I can see only Welcome to Home Assistant.
As Im new in this world…can somebody show me a way how to force Chromecast box to stream FUN TV to Samsung TV by default?