Transition effects usually appear when one slide changes into the next slide in a Slide Show.
- First, Select the slide to which you want to apply the effect
- Select the Animation tab
- Now, In the Transition to This Slide group you will see the transition effects
- Click on the drop-down arrow to see the menu of transition effects
- Select your desired transition effect
- Click on Apply To All to apply the effect to all the slides
See the image: