RSA 31:138: Election or Appointment.

I. The board of commissioners may be elected by the legal voters of the municipality at any meeting or election at which the provisions of this subdivision are accepted, or at any special meeting or election thereafter called for that purpose, and their successors shall be elected at each annual meeting or election thereafter in the manner or form as the municipality may determine.

II. The board of commissioners may be appointed by the mayor and board of aldermen or city council or by the selectmen of the town in the manner or form as the municipality may determine.