Enable Bluetooth on your iPhone. Then connect the iPhone USB cable to the proper cable extension coming from the device (USB1). CarPlay should now start without any further ado. (Else read the info provided on p.34/35 in the main device owner manual).

For a good read on the general function scope of CarPlay including an overview of CarPlay supported apps and additional information, go to the official Apple website: https://www.apple.com/en/ios/carplay/