You most likely have a switch or two, maybe three. The pump does operate 'on demand' when turned on, meaning it senses pressure drop in plumbing and kicks in until pressure is back to preset psi. If no switch, when tank was empty, you'd burn out the pump. Pump is also not needed when on pressurized hydrant at a campground.
The switches are often hooked together by an electronic circuit board that allows any of the switches to turn pump on or off, normally not possible in a 12 v DC circuit like 3 way 120 v ac circuits. The switches, as suggested, are usually near where water is needed, at levels panel, near bath or kitchen sink, toilet, even water bay compartment. In same area as water pump switch should be switch for water heater. (CAUTION don't turn on water heater until you are sure water heater tank is full of water)
By the way, most RV water pumps don't self prime, water flows by gravity from tank into pump. If an air lock forms in water line, it must be allowed to pass beyond pump for the pump to fill with water so it can pump.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI