How do you prime the oil pump?

I fabricated a pre-oiler from a propane cylinder based on some other homebuilt ones I saw on this site.
The 1/2" copper tube fits right inside a 1/2" pipe nipple. I epoxied it into the nipple. It sits about 1/4" off the bottom of the tank.
The 3rd fitting on the tank is a filler port.
I'll use it to prime the pump and also fill all the oil galleries