Yeah like DD said hook up a external pressure guage, standard light only registers about 5psi below anyway, enough so you know you've basically destroyed your motor, you want about 20psi at idle and about 10psi for every 1k revs after that.
Might need to prime the pump, I know aiden on here had that issue and had to fill the pump with vasoline first to allow it to start pumping. You should have oil pressure before the engine fires, pull the coil wire and crank it over.