Take the road to Selmun from the roundabout at the top of Mellieha hill. Take a sharp left 50m before the Chapel that is near the hotel & follow the one-lane (very bumpy) road all he way to the bottom. Be careful of traffic on the blind corners and think about taking your car down if its large as the rubble walls seems to shrink the road.
You need to do a 3-point turn to get into the access lane and as the parking area closest to the track down to the beach is clay, be careful where you park - especially after rain.