Hahaha, Trust me, took me over 2 years to figure that out myself. XD I set the ISO to lowest my camera will go (100), I had an f/stop of 1.8 (the highest the lens goes), I adjusted my focus on the light so that the camera would naturally darken the image, then tilted down to focus on her. That's roughly what I did, but again, trial and error. We had about 1.5 hours there, and we shot about 250-300 photos, probably half that are unusable.
I set the ISO to lowest my camera will go (100), I had an f/stop of 1.8 (the highest the lens goes), I adjusted my focus on the light so that the camera would naturally darken the image, then tilted down to focus on her. That's roughly what I did, but again, trial and error.