Changing carplay

How do you change apps on CarPlay to show different ones.
I can’t figure out how to make radio mute when I receive messages on phone

 

I can add or delete apps from device under SETTINGS. Not sure if audio mutes with incoming messages. I know mine will alert over music playing.

 

Mine mutes podcasts. Not sure about music.

 

mid you click the lower left corner of the screen it will display a “split screen” with the map and then whatever music/podcast app you are listening to. It will also display a couple of other suggestions automatically like calendar or if you have a garage door attached to home kit when you get close to your home it will automatically show that. I don’t think there is any way to change the displayed apps in the split screen setup.