The Concerned Citizens of Montauk has not only appointed Jeremy Samuelson as its new — and first — executive director of the 40-year-old environmental advocacy organization, but has also rented space for a walk-in office on South Elmwood Avenue, where the group hopes to establish a stronger presence in the hamlet. C.C.O.M.’s monthly meetings will now be held in the new space, whose walls will soon be hung with framed photo collages of days gone by and other artifacts.