My apologies I forgot the music part of your question.
In timeline mode you can drag an audio file -WAV, MP3, FLAC direct to the timeline from the file explorer in Photostory or Windows File Explorer and position it where you want to it to start and trim it if necessary.
The Movie templates & Editing templates have an option to add a music/audio file.
Note: when you switch a slideshow, that has been created using the wizard, to timeline mode it will be disconnected from the Wizard - you will get a warning message - one disconnected you can further edit the objects and effects if needed.