is this your system?
A) turn top right Valve handle should be pointed to 'TANK', meaning that you want to use your water tank with your water pump, or FILL the water tank(City Water is for when you are wanting to use the pressurize water and not from your tank)
B) bottom 'Winterization' Valve handle should be pointed to 'NORMAL', meaning that you are using your system normally, and not bypassing your Water Heater while in winterization mode(winter freezing)
C) connect your water hose from pressurized water to the 'Water/Antifreeze' hose connection
turn on the pressurized water to fill your tank
when full, or to the level you desire, turn OFF the pressurized water and disconnect
NOW, test this by turning ON your water pump and use your outside 'shower' handle to see if the water pump is supplying water from the tank
o.k., so I'm really 'guessing' here, but nothing else would make sense, UNLESS there is a valve(s) behind this panel area that are not seen in this photo... but I doubt it, though there is a big 'red' one on a standard pvc pipe that I believe is to 'drain' the tank.
The two other small 'low point drains' are to drain water from the interior water lines, cold and hot, before winterizing the coach.
note: check you water filter to see if there actually IS a filter inside....most of the time there is not, you add it once you purchase the coach... it should be in your 'initial owners box' of stuff. If not, it's a #8 size found many places.
Turn OFF any pressurized water/water pump, turn on your outside shower to remove any pressurized water, THEN spin the Water Filter off the housing mount. It may also be full of water.