To start metronome:
move mouse so pointer is over knob to right of metronome;
press down when pointer becomes a hand.
To stop metronome:
repeat "To start" instructions
To change tempo:
press desired number button on right for 40 to 200 beats per minute
with metronome stopped, move mouse so pointer is over slider on moving arm;
press down when pointer becomes a hand and move slider while holding
down mouse button—notice specific tempo changing above the  button.
Alternatively, select number above  and type in desired tempo.