how do you go about priming an lt1 pump in the car before you start it the first time???

 

You use an SBC priming tool on a drill while the intake is off (oil pump drive removed).

 

If the engine is in the car you need a right angle drill and then follow what shoebox said. Make sure the drill is on a high rpm setting.
Depending on the drill you may not see oil come up through the pushrods/rockers. Prime it for a few minutes and you may see it trickle to a few of them. Just make sure before you start it all your contact surfaces on your valvetrain has a generous portion of assy. lube or equiv. on it. That includes guideplates as well so you don't get a "squeak" sound once fired up.