How do I change the slide length in Storyline

Thanks, all (and hi Gerry), I mostly want to shorten the slides--on my last recording, some came in at over 100 seconds long (I don't know why--unless I was abducted by aliens for about a minute and a half), so it's kind of a hassle to drag the timeline.

For the course I'm working on, the slides advance automatically (regrettably).