The method is as follows:

1. First, make sure that the Bluetooth function of the Redmi 13 phone is turned on. You can turn on the Bluetooth function by pulling down the notification bar and clicking the Bluetooth icon.

2. Next, open the music player application on the Redmi 13 phone and find the local music you want to play.

3. In the music player, click the play button to start playing music.

4. Then, in the Bluetooth settings of the Redmi 13 phone, find the connected Bluetooth device (such as a Bluetooth headset or Bluetooth speaker), and click on the device to enter the connection state.

5. Once the connection is successful, the Redmi 13 phone will automatically play music through the Bluetooth device.