Damper

I have a new pappa bear stove and installed yesterday with a heat exchanger, does the damper go under or over the heat exchanger, seen pictures of it both here am puzzled.

You can put the damper where you like. By heat exchanger do you mean a "magic heat"? If so, they are frowned upon on this site. Do a search for magic heat. They cause a lot of creosote build. When flue gases fall below 212 in the chimney, the moisture condenses causing creosote, which will lead to a flue fire if not swept regularly (weekly?). A Papa Bear should make tons of heat without the "magic".
Edit: I just read your other thread, good advice from begreen and coaly.