When previews are enabled, the Special menu lets you view all the pictures contained in a folder or smart folder as a slideshow.
Select any of the folder’s pictures in the Special menu and choose Slideshow.
During the slideshow, use the controls at the bottom of the screen to pause and resume the slideshow, move forward and back through pictures, and view an index sheet of all the pictures.
To end the slideshow, click the Close control or press Escape.