How do you read a KSP delta-v map?

Each number on the map is the delta-v you need to get from one point to the next. Add up the numbers along your route and that's how much your rocket needs, plus a bit spare. So for a Mun landing: Kerbin surface to low orbit, then the transfer, then capture, then landing. Add them all up. If you're coming back, add the return trip too. The gotcha is that landings on planets with an atmosphere assume you use it to slow down. The stock delta-v readout in the VAB tells you what your craft actually has, so you can compare.