I'm watching Mr Happy's video on this (the only one I can find) and he mentions that a healer may be assigned to 'use the canons'.

So, on the off chance this could happen to me, just HOW do I 'use' a canon. What I mean is how do I interact with these things, I've never used any mechanical weapon in the game so what do I click/press/whatever?

Given there's no way I see I can experiment it'd be nice to have some clue before I'm expected to perform.