The app starts with a screen that lets you define the sections of your activity. The +/- buttons change the time value of the section. The control on the left is for minutes, and the other is for seconds.
The edit button lets you delete and reorder sections. The text field at the bottom lets you add new sections.
When your presentation is ready, tap the play button to start the timer.
Tapping anywhere on the screen pauses the presentation, and you can tap again to resume. You can also restart the activity from the beginning, or stop it early.
If you have switched to another app, or your phone is asleep at the end of a section, you will get a notification telling you the section has ended.
Pacing Timer respects your silent switch. If sounds are on, there is a "ding" to inform you of the end of the section. If your phone is set to silent, it will vibrate once to notify you.
If you want to turn off sounds and vibration, there is a switch in settings to do so.