If you plan to use an external display to show your presentation, you can use rehearse slideshow mode to set up the presenter display in advance, and to practice your presentation, without having the external display connected.
Note: If you already have the external display connected, simply play the presentation to rehearse.
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 customize the presenter display, move the pointer, then click 
.
For more details on modifying the display, see Customize the presenter display.
To rehearse 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.
Open or close a list of keyboard shortcuts: Press ? on the keyboard. You can use the shortcuts to control your presentation.
To stop rehearsing, press Esc (Escape).