I just got a power drill and a drill bit the size of the pvc your wanting to use and drill. I used 1/2 PVC, but i dont think it really matters. IT is pretty messy and I think I lost a lot of life on my rocks but it looks kool.After you drill the rock just slide the PVC through the hole and bingo. Also be carelful not to drill to close to the sides or the rock might break because it is very porus. One more thing make sure the weight isnt on one side or it might lean over.
Make sure you sort of plan out what your gonna do first, thats a biggy.