You did right by first sighting in the diopter to your zero (100 for you). Sorry for the "busy" photos!!!
Here you have the elevation assembly:
Loosen screw E and the range ring, F, will turn freely so you can set the 100 mark to coincide with the housing mark, K.
Here is the windage assembly:
Loosen screw F and the windage ring, G, will turn freely so you can set the zero mark to coincide with the mark on item H
Lastly, referring to the elevation assembly again, loosen screw J and position the pointer to the zero mark on the base.
And there, my friend, you have it!