Metronome settings can be accessed in two ways:
To change the speed of the metronome (bpm), tap the metronome button display at the far left of the control panel on the Tap Screen. A larger popup menu with a slider and stepper control allows you to change the speed from 15 to 300 bpm.  You also have the option to assign the same speed to all patterns in the current set. Press done to save the changes. On the Custom screen, metronome slider and stepper controls are available in the editing area.
To change the metronome sounds, use the Sound Options menu inside the Settings menu.