Arduino IOT Lightning Detector Kit Photo camera triggering

Hello,

I read the description but do not yet understand how I could hook up a camera triggering circuit.
I have hooked up a camera triggering circuit to an another arduino set-up using a transistor actuating an optocoupler.
Does this arduino have a spare digital output left.
How would I code the extra instructions to do that?

Can I simply connect it to the buzzer, (if the buzzer buzzes only at lightnings strikes)

Thank You very much!!!
Best regards
David