1st off, try not double posting
2nd, heres a nice tool for any1 (new and experianced users) http://www.getpaint.net/search.html It searches everything Paint.net!
Ok so you need help with blending...
You could simple just add a new layer, copy the doll, reposition it and move the top layer down..
If you want it to look like it was "THERE" and not just pasted on top your going to need to be a little bit more specific. Maybe post the doll, and a pic or two you want it in. And what exactly you need done , I would be happy to go step by step how to blend or add the paper doll to the picture for you Im leaving in about an hour so the sooner the better