Unscrew the forward cover underneath the passenger side bed. Underneath is the fresh water tank and the pump. Towards the centerline is a PVC pipe that leads to a 1/4 turn PVC ball valve and then down and out of the coach. Turn it a 1/4 turn and it will dump the tank.
I assume you are winterizing. In the forward centerline side of that compartment is a small three way valve almost hidden by the tubing and hose. Turn it 1/4 turn and it blocks flow from the fresh water tank and picks up from a 1/2" hose teed into the valve. That hose has a 1/2 NPT plug on the end. Unscrew the plug and get a 1/2" male NPT x 3/8" hose barb fitting from your hardware store with about 3" of tubing. Connect the tubing to the hose with the barb and a hose clamp. Then drop the other end of the tubing into a jug of antifreeze, turn on the water pump and a water fixture and the pump will suck up the antifreeze from the jug.
One by one turn the cold then hot water on on each fixture until you see pink stuff coming out. Don't forget the outside shower and the toilet flush. Then dump a cupful of antifreeze into the sink and lavatory drains to fill the trap. Dump a couple of cups into the shower and toilet to antifreeze the tanks, but make sure they are really empty before hand.
This takes about 2 gallons of antifreeze to do they whole coach. Oh and don't worry about the Girard water heater. Just flush it with antifreeze as you do the hot water fixtures. Best to turn it off first using the switch underneath the outside cover.
Here are some pics of the tubing (yellow arrow) and the 3 way valve (red arrow) and the jug of antifreeze hooked up: