Two ways to winterize. Blow the water out of the pipes with a compressor set to about 40 PSI. Need an adapter to put air in the water inlet. Or secondly to use the water pump to push RV potable antifreeze through the pipes. Typically an adapter is added to the pump inlet. Don't put the antifreeze in the fresh tank.
Fresh tank should have some room for freeze expansion as long as it is not 100% full. Or possibly it is in a heated area of the RV.
Not sure how cold you will be tonight but you might make one night just running the space heater but the odds might be slim. If you do, make sure the water heater is full and turn it on.
Check with the office to see if they have anything that may help.
Good luck.
