You cannot from what I can see. You can add residents to GL, WW, and NL towns, but NH towns do not have an add residents option like the others. If you know how to add residents to NH towns, please let me know how.
In my original NH town, I was able to add residents. I have since deleted that town since I got a new switch and I created a new town. When I add the new town, I am unable to add residents or anything to the museum. So why did it work before but not now?