Replacing thermostat

I've got a new thermostat to put in the housing, and can't figure something out. When I took the old one out it fit pretty snugly. I just seemed like it had a place to go and sat there nicely. Now that all of the old gasket material is gone from the housing, the new thermostat doesn't really fit anywhere. It just sits there without being held in at all. Will the gasket sealer take there of that problem? Or do I have the wrong thermostat?

Also, how do I go about putting this on? Just put the thermostat in, then put some sealer on there followed by the gasket and bolt it on to the engine?

This is a 4.0 correct? If so, you should have a recessed area in the housing the t'stat fits in, then the gasket holds t'stat in place, line up the holes and bolt it on. Make sure the t'stat stays in the recessed area or when you bolt it down it will crack the housing.

yeah, the engine side surface of my thermostat housing is completely flat.

The edge of the thermostat opening in the head should have a slight recess that allows the t'stat to seat correctly. Make sure there isn't any gasket material or RTV in that recess preventing the t'stat from seating.