You can use a regular circle or whatever shape you’re using, and after typing on the path and centering your text, you should see a “stick” coming out of the top of the circle. Drag that into the circle while making sure it stays centered and you should be good!
If you want it specifically on the outside of the circle, after you do that go to type > type on a path > type on a path options, and chose ascender (or however you’d like it positioned) and then you could set the baseline shift in the character panel to align it perfectly to your shape.
That sounds confusing, but it’s really not 
Good luck!