New Supervisor vs. Staff, help please?

u gather them all including david and write on board their commitments and let them put the rules .. working hours .. reports timing ... dept meetings ... what are the ideas that would make the dept better ... etc ... the point is .. take the commitments from their mouths .. also while doing so , show the main rules of the place which you can't cross .. no one would say something creepy .. specially david -on the contrary- let them speak up their commitments and agree on it and make sure u r the first one who will follow it ..