Instructions: On/Off: Turn the VOLUME knob clockwise and turn it on; Turn the VOLUME knob back-clockwise and turn it off. When you turn it on, you can control it by the remote control ON/OFF. AUX Mode: The default state of the first power on is AUX mode. If you do not have a power outage, it will automatically return to pre-off mode, such as USB, SD/MMC, AUX, FM, BLUM (Bluetooth) etc. When you connect the external audio source to RCA input, press the MODE button to enter AUX mode. Press the MODE button again or insert USB, SD/MMC card to enter another mode. Mode change: Mode button allows you to choose the mode If the USB / SD / MMC card is not inserted, the mode selection order is AUX, FM, BLUE. Volume Adjustment: Volume can be adjusted with VOLUME knob. You can also adjust the volume + or volume button on the remote control. Bass Control: Treble knob to adjust treble and bass control with Bass knob.