For example, if you want a song to play on the Pop station, you would put the file into Custom Music > Pop. Putting music directly into the Custom Music folder won’t work, nor will creating a new folder. You’ll need to pick a preexisting genre.
You can’t make a shortcut to the audio file - the game can’t read it.
You may have to adjust the stereo’s volume to hear the music. Some players can find and test their custom music by accessing Game Settings, and then clicking the Music tab. However, other players report the file not showing up, or showing up with a blank name. If this happens to you, test it on the stereo.