You can enlarge (zoom in) or reduce (zoom out) your view of the slide canvas.
Choose View > Zoom > zoom level.
Choose a magnification level from the Zoom pop-up menu at the bottom left of the slide canvas.
If you’re using Keynote on a Mac with OS X Lion (v10.7) or later, you can also view the application window in full-screen view, to help you work without distractions. To learn more, see Full-Screen View.