You can change the BPM on the app by using the BPM wheel or by entering a BPM number with a numeric keypad.
Entering the BPM numeric will allow you to quickly set the BPM to the intended number.
This is how you do it:
Step 1. Go to Metronome page and click on the BPM
Step 2. Enter a number between 20 and 400 to set the BPM and press Done.