Really low oil pressure

[latof]

My friend rebuilt a 6 bolt block for the one that blew up in my 95 gsx. So we swapped out the engine, and now i have really low oil pressure. He says he is sure that he forgot to do something with the bolt to the crankshaft that allows oil to flow through it. I was wondering what that bolt is called, and what i would have to do to get at it and what to do to it in order to make sure my bearings don't wear on the crank and blow the engine up again. please post pictures if you have any idea what i am talking about.