• When you click the mouse during a slide show, an effect starts playing by default. If you have numerous effects, you'll have to click several times to start each one separately. You can have effects that automatically play at the same time or one after the other by altering the start option for each effect.
• Select an effect from the Animation Pane. Next to the effect, a drop-down arrow will appear.
• Use the drop-down arrow to select an option. There are three different ways to begin:
• Start on Click: When the mouse is clicked, the effect will begin.
• Start With Previous: This causes the effect to begin at the same time as the one before it.
• Start After Previous: When the previous effect finishes, this will begin the effect.
• Choose the appropriate start choice.
• All of the effects will go through automatically when you preview the animations. You'll need to run the slide show to test effects that are set to Start on Click.

Read More: What is the use of notes pane in PowerPoint?