If you are in the Metronome or in Create Rhythm you can simply shake your smartphone to reset the rhythm back to a standard 120BPM with 4/4 time signature. You can turn this functionality on and off in the App Settings.
If you would like to set the BPM manually, you can tap on the BPM number and Enter a number between 20 and 400 to set the new BPM.
If you create a new rhythm in the Library tab the default setting will automatically match what you currently use in the Metronome tab. This makes it easy to save rhythms you just played with!
If you are in the Library you can simply double tap on a rhythm or setlist to load it in the Metronome.