Help me with timing

I have a 92 camaro with a 3.1L engine. We blew the engine the camaro origionally had so we put in a new one and have it to the point where the engine cranks but won't start. I'm almost positive it's a timing problem but i'm not sure exactly how to set the timing. Everyone tells me about all of these marks there are supposed to be on the pulley and the distributor but i'm confused. How is it that you set the timing on a car when there are no marks to tell you where to line up the distributor or anything?