1. First, you need to determine the power source type of the four-wheeled vehicle, whether it is battery-powered or plug-in powered.

2. If it is powered by a battery, you need to purchase an adapter to convert the music player's power supply to the same voltage and current as the four-wheeler battery.

3. Connect the audio output cable of the music player to the audio input port of the four-wheeler (if there is one). If the quad bike does not have an audio input port, you need to find the audio input port on the quad bike's audio circuit board, and then connect the audio output cable of the music player to that port.

4. After the connection is completed, open the music player and play the music, then adjust the volume and tone (if any) on the four-wheeler audio circuit board until you get the best sound quality and volume.

It should be noted that safety issues need to be paid attention to during operation, especially when connecting to the power supply. At the same time, it is also necessary to ensure that the quality and power of the power adapter and music player meet the requirements of the four-wheel vehicle to avoid damaging the four-wheel vehicle or causing safety hazards.