For information on how to access your client panel, see this article.
In the Client Panel, you can change the music options in the "Settings" tab by scrolling down to the "Music" options below the "Tour Title" option.
You can listen to the music options to find the one that best meets your needs. To listen to the music selections, highlight one of the songs, and press the "Play" button (the triangle). To stop your music, select the "Stop" button (the square).
Once you have chosen a song that you would like to use, highlight the desired choice and scroll down to click on the "Save" button (below the "Statistics Email" box).