Because the water systems is where all water enter's the coach (including drinking water), many of these steps are to insure that the ends of hoses don't get dirty from the ground and especially from contamination from the grey and black waste water.
Turn off water pump (at any of the buttons near sinks inside or the switch in the wet bay outside)
Open the wet bay and remove the left drain cap (under the shower station)
Drop the green hose through the drain hole
Connect the white drinking hose to the water faucet and the green hose
Turn the water on slowly at the faucet
Check water inside
* NOTE * If the outside shower faucets are on in the wet bay, hot water will be reduced inside the coach. When off, the shower will not spray when the trigger is pressed.
Turn off the water faucet
Disconnect hose from faucet end (will likely spray a little as pressure is released)
Disconnect
Turn on the water pump using one of the three methods below
Turn on the switch in the wet bay
Click the button in the middle lavy labeled "water pump" until it is blue
Click the button in the back bathroom labeled "water pump" until it is blue