BTW, if you mean prime the engine with oil - it is an engine oil priming shaft.
If you are talking about priming the oil pump after the pump has been assembled (before hand they say to pack the pump with Vaseline) just remove one of the oil cooler lines and pour oil in the line. I do not believe that it is necessary to do either as the oil pump will suck the oil out of the pan and begin the build pressure within three seconds in my experience.