Those are ordinary composite video inputs, which isn't really any good when it comes to quality. Way better than using the antenna signal of course.
I was hoping that the "VTR" connector had som RGB input, which would be the best. But unfortunately it seems to be a parallel input to Line B, but with the audio signal combined.
Anyway, connect pin 1 (Composite) and 2 (GND) from the Genesis A/V connector any Video in BNC on the monitor.
The audio signal is from pin 3 and that should go to the audio input at the monitor (with ground of course).
http://pinouts.ru/Game/sega1_pinout.shtml