If the audio unit has a Bluetooth input, just pair the two and select that input for audio output on your car. If it doesn't have a BT input, then you can get a BT adapter but you'd have to know which interface your car unit uses to do that (if it doesn't have AUX, it might be connected via RCA to the panel). Or you can get a Radio Transmitter that hooks up to your phone's headphone jack and transmits to a certain frequency which you can tune your car's system into (not ideal, this usually means a bit more noise than a BT or wired connection).