How to shuffle photos (random order) in slide show?

The Help of my iPhoto says I can somewhere set an option to make the slide order of photos in a slideshow be random (shuffle). I don't see this in any of the menus! The help says

"Click Settings at the top of the Slideshow window to set one or more of the following options:"

my Settings are at the bottom, not at the top, and I see all the other choices (music, transition effects, etc.) but nothing about play order. Am I missing something?

Mike