So i'm an idiot and i don't know how this fitting goes together. How do you get the probe to stay in the fitting w/o coming out. There are 4 pieces to the fitting:
-the NPT part that threads into the manifold
-a conical piece
-a washer
- and the cap that goes over everything

the npt part has a conical inside
so how does this all go together?

It's a standard compression fitting. The conical part goes between the NPT part and the cap. Look inside the cap to see which direction it goes. Insert the probe and tighten the cap down and it will lock the probe in place.

Tony