Either call Dish tech support 1-800-333-3474 or go online and do a chat session with a rep.
Tell them you are in an RV and want to change your "SERVICE" location (not your "billing" address) and you want to get local channels. All you need to give them is the zip code where you are located. Some reps will ask for a full address - they do not need it!
You can also go to
Satellite Guys Dish spot beam maps and find the spot beam you want.
For instance, in June & July we were traveling around Oregon. I saw that the Portland beam covered the entire state so I gave them a Portland zip code and then had Portland locals for the entire period.