The reflector should be 1/4 or 3/4 or 5/4 or 7/4 wavelengths from the back reflector, and as close to the dish's focus as that allows. ideally you'd use a dipole antenna at the end of a feed coax, but you can try just placing the whole module there. Make sure the antenna wire is perpendicular to the axis of the dish.
Then experiment a bit !