Hi and welcome...
What is the specific model of your trailer?
For the part of the world we live in blowing the lines with an air compressor (25psi), dumping some RV antifreeze in the drain p-traps and making sure the water heater is empty is about all we need to do.
If you want to run anti-freeze in the lines you will need to find the pump, some of them already have an adapter with a valve that will allow you to pull anti-freeze from the jug, otherwise you have to pull the suction line off and use a short line between the pump and the jug.
Usually the pumps are pretty close to the water tank. Look in the general area where you put water into your trailer. It may be under a seat or behind a panel somewhere. On my camper it happens to be under the wardrobe on the front left side. Every one is a different.