First, ensure your holding tanks are empty, then close the drain valves.
Then looking at your water pump, you should see a hose coming from the water tank to the pump and a hose not connected to anything going to the pump as well. There will be a valve at that 'T' fitting. Turn the valve so that the handle is in line with the tube that doesn't go anywhere. Stick that tube into your jug of antifreeze, turn the pump on, and it will start pumping anti freeze all through your camper. If you have elected not to bypass your water heater, go outside and hold the pressure relief valve open until you get solid pink coming out of it. Then go to each sink and open the faucet handle for cold and hot. Start with the sink closest to the pump. Leave the valve open until solid pink comes out, then close it. Go to the next closest one and repeat. Keep an eye on your antifreeze jug, that stuff will pump out fast. After the sinks are done, do the shower (don't forget the outside shower) and the toilet. Turn off your pump and remove the antifreeze jug. Pour about a cup of antifreeze into each sink and shower drain. Then pour some into the toilet without flushing. That will help your flange seals stay soft.
2014 Coachmen Catalina 253RKS
2016 Keystone Summerland Mini 1750RD
2012 F250 Lariat 6.2L Crew Cab FX4
Reese dual cam SC/WDH