Follow the steps in the support document you posted from.
If you are having a specific issue, then you'll need to explain what that is.
- If your car supports CarPlay with a USB cable, plug your iPhone into the USB port in your car. The USB port might be labeled with a CarPlay icon or a smartphone icon. Be sure to use an Apple Lightning to USB cable.
- If your car supports CarPlay both wirelessly and with a USB cable, plug your iPhone into the USB port in your car. An alert on your iPhone will offer to connect you wirelessly on your next drives.
- If your car supports only wireless CarPlay, press and hold the voice command button on your steering wheel. Make sure that your stereo is in wireless or Bluetooth mode. Then on your iPhone, go to Settings > Wi-Fi, and make sure that Wi-Fi is also turned on. Tap the CarPlay network, and check that Auto-Join is turned on. Then, go to Settings > General > CarPlay, and select your car. Check your car manual for more information.