How do I turn on/turn off the Metronome?

Answer:

Click the button labeled “CLICK” (for “click track”) on the bottom left side of the Session window to change its state from On to Off or from Off to On. To hear the metronome, the Leader must click Play to start the transport and all members of the Session will hear the metronome in sync.

You can also use the Knob to adjust the volume of the click track.