You get out of the place you got them in and go left the Warp Pipe. Then go right a little and there are 2 big rocks that you put the Moon Stone & Sun Stone in. 2 blue switches will appear. Put Koops on 1 side and hold him there. Then you go to the other switch let Koops go and then use your hammer. It will reveal the path to Hooktail's Castle.
pokemaniackid