I'm not sure which area you are talking about. I had to put gear oil in both gear boxes on mine. I have a King Kutter, but it is branded Rural King. I assume they would basically be the same. You have a weep plug on each gear box that you remove and then fill until it weeps out. I found with the middle gear box, I can just look down into the fill hole and the gear oil should just cover the gears, making it unnecessary to remove the weep plug.
You have to also grease the bearing on the end of the tiller.