How to Create a PowerPoint 2013 Slide Transition
Select the transition you want to apply from the Transition to This Slide section of the Transitions tab on the Ribbon.
If you want, you can display the complete gallery of transition effects by clicking the More button at the bottom right of the mini-gallery of transition effects displayed within the Ribbon.
Note that when you select a transition, PowerPoint previews the transition by animating the current slide. If you want to see the preview again, just click the transition again.