Press U (or select Presentation > Storyboard).
The Storyboard interface appears near the top of the window.
To play the current slide, do one of the following:
If you are in side-by-side view, press Ctrl+P to play the current slide in the left view, and press Ctrl+Shift+P to play the current slide in the right view.
To play the next or previous slide, or the first or last slide in a storyboard, use the controls that appear at the top of the Storyboard interface or the following hotkeys:
If you are in side-by-side view, press Ctrl+left to control the left view, and press Ctrl+Shift+left to control the right view.
If you are in side-by-side view, press Ctrl+right to control the left view, and press Ctrl+Shift+right to control the right view.
If you are in side-by-side view, press Ctrl+up to control the left view, and press Ctrl+Shift+up to control the right view.
If you are in side-by-side view, press Ctrl+down to control the left view, and press Ctrl+Shift+down to control the right view.
As the slide plays, a play indicator appears.