To create interval bells, simply:
1. Go to Library, then select Timer.
2. Under the Timer tab, select Interval Bells.
3. Click on + Add Bell and Choose the Bell type.
4. Select 1, 2, or 3 bell strikes.
5. Choose either the bell to sound 'From start' or 'Before End'.
After you have added all of your interval bells, make sure to tap Save to save your intervals.