There should be a spigot on the underside of the trailer on the fresh water tank. Turn it to open and drain. Just remember to close it again when it is empty.
There is a fresh water inlet on the side of the trailer. Just open the door and stick a hose in. It will be near the city water hook up.
'09 F-350 6.4l Crew Cab
'10 Komfort Trailblazer T262BSLE