CarPlay is not another app, is just an extension of your current iOS app. You can not install “The CarPlay app.”. If you have experience developing apple watch apps you will be familiar. Everything runs on the iOS device, so you still have access to most of the iOS resources. It lives on the ram of the device, you can play a lot with it but you have limited and strict displays.
repo https://github.com/shadowmanpat/Apple-Car-Play
You should read the detailed Apple CarPlay programming guide.
https://developer.apple.com/carplay/documentation/CarPlay-App-Programming-Guide.pdf
and https://developer.apple.com/documentation/carplay
Also, a good example of showing custom displays on the CarPlay screen
https://developer.here.com/documentation/ios-sdk-navigate/4.11.3.0/dev_guide/topics/carplay.html
but still, you have to request Apple for development in order to run on a real device
https://developer.apple.com/contact/carplay/
As you can see, CarPaly capability is available on the App ID Configuration page.
