If you've gotten the hang of Kerbin orbit, getting to the Mun, and getting into orbit around the Mun.... but just struggle with the actual landing. I'd highly suggest the use of F5 (quicksave) and F9 (quickload). Hold F5 before beginning your descent to the Mun, if you crash, press F9, rinse and repeat. It'll save the frustration of having to redo all previous steps, every time you crash.