Add more than one song to the soundtrack of a Magic Movie project in iMovie

I have created a Magic Movie from a number of photos and added a song as a soundtrack. I wish to add a few more songs as it is a 12 minute project and it currently plays the 2 minute song over and over. In the edit screen, it simply lists all of the photos that make up the project and I can't work out how to change the view to be able to add multiple music tracks like in a movie project (or is there another way?)