These days, a lot of higher-end RVs have water management panels such as the Nautilus P1. While they do make water management tasks easier, it can sometimes be confusing on how to winterize them. This page then attempts to make the winterization process easier to understand. Note that this page and attached video should be used as a reference only - you should follow the winterization instructions from the manufacturer.
If you do not have a copy of the winterization instructions, you can download them here, The winterization instructions begin on page 9.
There is no need for me to replicate the instructions, so I will provide you with a few comments.
I also run a bit of antifreeze into the fresh water tank with the Sanitize function - which can also be found in the instructions. Finally, I pump a bit of antifreeze into the black water rinse port. As well, this is not covered in the instructions, and I was not happy with blowing air into the port as I could not tell if the water was completely removed or not. There is an anti-siphon valve in the line so the only sure way I have to ensure the line is protected is by pumping in a bit of antifreeze.
The antifreeze jug I used came from a Camco 65501 "Do It Yourself Boat Winterizer Kit. I modified the kit a bit by shortening the hose so it would be easy for the pump to maintain prime. A hose adapter can be found at most well-stocked hardware stores.