Press ESC in the game and change Basic to user-defined.

Then you can select the music you want to add in the list and double-click it to add the song.

If the module for adding songs does not appear after selecting user customization.

You can manually call it up as follows:

Find a small button with music characters on the mini map in the upper right corner of the game screen,

click It will pop up to add a music template. The last button in the template is used to find the music file directory.

You can try the above methods