The tank flush is simple. Empty the black tank, leaving the valve open once empty. Connect a water hose to the tank flush port and pressurize the hose. The spray port in the tank will wash down whatever it is pointing at. They say to only run it with the dump valve open.
The cable may be tricky, since yours doesn't appear to be labeled. Look closely at the brown plate to be sure there isn't a label molded into the face. If not, typically Alliance makes the top connection for satellite and the bottom for cable. Someone correct me if this isn't so in the Delta line.
For cable, connect the campground system to the cable port. You should have a cable feed at each tv location.
Satellite won't be hooked up behind the panel, but there are coax cables there that run to each tv location. You decide where you want your receiver and hook up that cable.
I hope this helps. I believe they are working on the owners manual for the Delta line.