For much of North America, you need to prepare your RV for winter storage. The water system is the most important aspect because you don't want to dampen the excitement of spring with broken water lines or cracked water heater.
You should consult your owners manual for specific steps for your rig. Just in case you have special systems or unique steps to do so.
Remove all inline water filters and bypass them. This is because you don't want them to freeze up and you also do not want to put anti-freeze in them. Drain the fresh water tank. Drain and flush your grey and black water tanks. Your last camping trip of the year is a good time to do that part.
Make sure the hot water heater is off and cooled. With water unhooked and pump off, open a hot water faucet to release pressure. Drain the water heater by releasing the pressure relief valve and then remove the drain plug.
Open all water faucets, hot and cold. Open any other valves like on the toilet, shower, outside shower and faucets. Look for the lowest water point in your lines, most likely the outside shower or in the outside water compartment. Use the water pump to run as much water out as you can. Turn it off as soon as water stops coming out. You can then close all the open drains and faucets.
Hopefully you have a water heater bypass. Very handy to have because if you do not, you would be filling up the water heater with RV antifreeze before it ever gets started into the water lines. That is however many gallons your heater holds.
Your RV might have a bypass to feed antifreeze into the water system with the pump. If not, you need to disconnect the inlet side (from fresh water tank) of the water pump, attach a hose or tube and run the other end into a jug of RV antifreeze.
Turn the pump on to pressurize the water system. Go to the closest faucet to the pump in the system and open both side until the pink fluid starts flowing. Close the faucet. Then go to the next closest faucet and repeat for all. Remember the inside and outside shower as well. Flush the toilet until the pink fluid appears.
Pour a cupful of antifreeze down all drains. Pour some in the toilet and the shower drain too. Then double check to make sure all faucets are closed.
Remember to think about any specialty systems you may have like solar water systems, ice makers, dishwashers and laundry machines. These are not as common and your RV should hopefully have manuals on them and mention draining.