In PowerPoint 2010 and 2013, you’ll find controls in the lower left corner of your screen that you can use while showing your slides.
In 2010, you’ll see Previous Slide (left arrow), Arrow/Pen Tool options (pen icon), Right Click Menu/Options (right-click icon) and Next Slide (right arrow). In PowerPoint 2013, Next and Previous slide icons are adjacent, and they’ve added a Show all Slides button and Magnify. Magnify is great for complex charts and graphs. Hover over each one to activate it, and then click. Many of these are accessible by, as well.