Take the cap off the sewer fitting on the trailer and one end of the hose will connect to the trailer, leave all valves closed. The piece that's threaded will connect to the opposite end of the hose away from the trailer. If the sites a full hookup site you need to take the cap off the fitting in the ground. The threaded piece you have connected can be screwed into the ground fitting and if it is not threaded just put the end in the fitting and a rock or something to see it doesn't come out. When you dump pull the black tank valve first followed by the gray valves. Disassemble and stow when leaving.
Ground end