When you play a presentation in Rehearse Slideshow mode, you can see the current slide, your presenter notes, and a clock on the screen of your Mac. This view makes it easy to rehearse a presentation.
You can add items to your screen, such as a timer and the next slide, and you can modify their layout.
Open the presentation, then click the first slide.
Choose Play > Rehearse Slideshow (from the Play menu at the top of your screen).
The presenter display appears.
To see options for customizing the presenter display, move the pointer, then click 
.
To advance through the presentation, do any of the following:
Go to the next slide or build: Press the Right Arrow key.
Go back a slide or reset the builds on the slide: Press the Left Arrow key.
Jump to a different slide: Press any number to make the slide navigator appear, enter the slide number, then press Return.
To open or close a list of keyboard shortcuts you can use to control your presentation, press ? on the keyboard.
To stop rehearsing, press Esc (Escape).