Hope you have had all the relevant health tests done on your dog and made sure the b!tch has too.
Stud work is not that easy especially for novice owners/dogs. Some females will stand every day of their season, others only on a certain day. If she is not ready an experience dog would not bother with her, and she might have either gone past her time or not quite be ready. I would definitely not let them loose to see what happens, she may bite him or if they do mate and tie she might damage him by pulling away and trying to get away from him. Has she been premate swabbed by the vet? There is also the chance of infection to your dog if she is carrying anything. As for the dog knowing what to do, not all do! You might have to assist and at this point either the dog could lose interest, or bite you, or the female might bite you. Ihope you are not charging for this as he is obviously an unproven stud and I would not want to be paying for the service unless you/he knew what you were doing.