Van ran hot stopped instantly and now will not crank

This is never a good story. Remove all the spark plugs and squirt a little oil in all the cyclindersthough the spark plug holes. come back tomorrow after it's had pleaty of time to soak in. try to turn the motor by the crank pulley with a socket and a breaker bar try to turn it in either direction, if it turns try to turn it all the way over in both directons. once turning you can try the starter ( with the plugs still out) oncwe turning over quickly put the plugs back in and start it, Look into the reason for the overheating right away and find and fix the problem. If it still doesn't turn you can try harder by removing the starter and putting a prybar on the teethe of the flywheel and pry the motor to turn ( try both ways) if it's still locked the liklyhood of having a repairable engine is low and go shopping for a replacement motor. Or a replacement vehical ( might be cheaper.)