set the rod at the ring opening,you can open /close the ring for trigger sensitivity,,the feeder sits between the "y" piece of the trigger.
i have one and seen the squirrel hanging upside down from the top and it has triggered it and the door has folded inwards to close but hit the squirrel on the back and it just moves away,to be honest not had any success with it but im gonna persevere. did you not get instructions with it? if you want a copy pm me your address and i will pop a copy in the post for you.