You can also download a PDF of the 2020 owner's manual for Freedom Express Ultralight trailers at this link. They have one manual for all of those floorplans and not for each such as the 257bhs. I was hoping it would show the anti-freeze pickup hose in a photo but it does not. It does however show photos of how to set the bypass valves for winterizing and you will need to know that at some point. That info is on page 37 and 38 (by the page numbers at the bottom of the pages, not the actual PDF page number):
https://s3.amazonaws.com/cd-content....b5ec2abba9.pdf
The hose on the water pump should have a 3-way valve where it connects to the other water lines. In one position, the water pump sucks water from the fresh water tank or the city water inlet, in the other those are locked out and it sucks from that hose, which is meant to be inserted into a gallon jug of pink RV antifreeze. That way you can use the least amount of antifreeze instead of putting it in the fresh water tank (which will take a lot more). You also want to drain and "bypass" the water heater before winterizing. It has valves for that also.
From looking at the floor plan and photos of the outside of that model, your water heater is on the back wall. Outside you will see a black door, that is it. Inside it is most likely under the plywood for the bottom bunk in the bunkhouse area and against the back wall. You may be able to see it if you look way in the back of that storage compartment via the door at the front, but to actually access the rear of the water heater, I think you will have to lift up the plywood under the bottom bunk.