It pops open and snaps closed by fingers, it holds strong enough to not open on its own but isn't too hard To open.
Find the segment of the ring right before the little hinge and pull it up.
If you look close the hinged piece has a little dome shaped ball at the end and it snaps in the rest of the ring.
Grab the hinged segment of the clicker ring, slide it up to meet the other edge of the ring and “snap” or “click” it into place.
All clicker rings have a hinge and segment that is easily hidden when closed.