Municipal water doesn't go through the pump, so there should be a "T" fitting (or possibly a "Y" fitting) a short distance downstream from the pump, with one inlet coming from the pump, and the other from the municipal water connection. Placing the filter immediately downstream from that fitting allows you to filter all the water you use, including the hot side since it's upstream from the water heater.
As for where to install it, I can't answer that due to a lack of familiarity with your exact floor plan. But make sure you've got access so that you can change out filter cartridges without creating a water leak. You may only be changing filters once a year given typical RV usage, but you'd want to remove the filter cartridge before adding antifreeze anyway so you might as well set it up to be as easy as possible to reach what you need.
I thought getting old would take longer!