Hold down the [SOURCE/PWR] button for less than 1 second until the Bluetooth Audio mode is shown.
For details, Switching Audio Modes.
Press button [1].
The connected Bluetooth-compatible portable device starts to play music.
If the portable device is not connected to the main unit, its play function is disabled.
If audio play does not start even when you press [1] button on the main unit, press the Play button on the portable device.