You have to drill a rock socket, install the pile, and then fill the socket with concrete. The socket can be drilled in various ways. You can use a crane-mounted drill with a rock auger, core barrel, or down-hole-hammer. You may be able to use a hydraulic backhoe equipped with a drill attachment such as a Lo-Drill. You may be able to use a track drill with a down-hole-hammer. How you drill the socket can depend on how many sockets you need to drill, how much overburden you need to drill through, how hard and drillable the rock is, and if the overburden needs to be drilled using a casing pipe that has a larger diameter than the socket. Loose overburden soild and/or high ground water may require a casing pipe to be used just to drill down to the top of rock.