Use the data cable to connect the mobile phone and the car mp3 player, put the songs in the mobile phone into the music folder, and the songs will be automatically recognized and played.

We need to turn on the Xiaomi 4 USB debugging mode switch through the following methods.

Method/Steps

Enter Xiaomi 4 desktop, find the "Settings" button and click to enter the settings interface.

In the "Settings" interface that opens, flip to the bottom of the settings interface, find the "About Phone" item and click to enter.

From the "About Phone" interface that opens, find the "MIUI Version" item and click it seven times in a row to turn on the "Developer Options" function.

Next, return to the "Settings" interface, find the "Other Advanced Settings" item and click to enter.

At this point, you can find the "Developer Options" option in the "Other Advanced Settings" interface and click to enter the "Developer Options" interface.

Finally, in the "Developer Options" interface, turn on the two options "Turn on Developer Options" and "USB Debugging". The "Allow USB debugging" window will pop up. Click "OK" to successfully enable the Xiaomi 4 USB debugging mode.

Then you can use the USB data cable to connect Xiaomi 4 to the computer normally.