Changing menus on Sansa Clip Zip

How do I change menus on my Sansa Clip Zip? I didn’t see it explained in the Guide Book. If I want to change from the Music menu to the Audio Book menu, for example, how do I go about it? Also, in the music menu, how can I quickly go to another one of my preset radio stations? Thank you for your patience. CE

Press the right or left buttons.