In the Bluetooth screen, you can select 'Add New Device' and then select the Google Pixel (assuming that the phone is set to broadcast that it's ready for pairing).
Once you see the PIN on the Tesla's display show up on the Google Pixel, you can pair the phone and car together over Bluetooth.
Bluetooth connections to a car can sometimes be troublesome so Tesla includes some Bluetooth Troubleshooting Tips in case you get stuck or have problems.
Once your phone is connected, you can see play any audio from the phone. By default, Google Music will start playing but you can also play music and sound from other Apps like YouTube and Netflix.
One of the nice features of pairing with an Android phone with Google Now enabled is that you can say outloud 'Ok Google' anytime through the Tesla Model X's audio system and Google will be able to respond to your voice commands and queries (although you won't be able to perform any non-audio car controls like navigation, climate control, etc.).