Winterizing TM in upper midwest

Hi, we are relatively new TM owners in southeast WI who have had their unit a couple of years. We are getting ready to winterize this year and were wondering what others in a similar climate are doing. I have opened all the low point valves (I think) and ran the pump until it sounded like it ran dry and no more water came out of the drain underneath. I know the dealers all say you should put antifreeze in the system but am not sure how to do that. Do you pour it in from the city water hose access and run it through with the pump and how would you do that? Thanks, James.