Take the Mass Pike Route 90 to the end, in Boston. Go south on Route 93, the Expressway. Take Exit 12. It probably says "Route 3A, Neponset, Quincy". Keep right off the exit, and go straight through a rotary and lights, to put yourself on the Neponset River Bridge. Stay on this main road. It becomes Quincy Shore Drive. After crossing the bridge, in about a mile, you will see the beach on your left. There are two yacht clubs on the beach, on pillars in the water. I think it is the second one on your left. You can park on the left, along the beach (carefully, 4 lanes of traffic.)