Most campgrounds have water hookups. Just plug your white hose into their spigot and fill your tank when you get there. Not a bad idea to put a filter in-line - - you never know what minerals or other fun things are in the local water supply.
oh, and NEVER fill from the dump station, even if there’s a spigot there labeled drinking water. When I had an RV, I lost count of how many idiots I saw using the drinking water hose to backflush their sewage tank.