You can add notes to any slide to help you present. You can refer to your presenter notes during your presentation if you’re showing your presentation while connected to an external display. In this case, you must set up the presenter display layout to show presenter notes.
Click View 
in the toolbar, then choose Show Presenter Notes.
Type notes in the white area below the slide.
To change the font size or apply text formatting to the presenter notes, use the controls in the sidebar on the right. (If you don’t see a sidebar, or the sidebar isn’t labeled Presenter Notes at the top, click 
in the toolbar.)
To hide presenter notes, click View in the toolbar, then choose Hide Presenter Notes.
You can view your presenter notes on your screen while showing your presentation on a connected display. The notes appear only on your screen, so only you can see them.
Click 
in the toolbar on your Mac, then click 
.
Select Presenter Notes.
To move the presenter notes, drag them.
To resize the presenter notes, click the item, then drag any selection handle.
Press the Right Arrow key or the Space bar to advance through your presentation.