Welcome to Cruise-Chat. You can't make reservations prior to boarding the ship unless you're in a group. Then your travel agent would make the arrangements. You can go to either Portofino's or Chop's entrance and reserve a seating for any open night. You may also see a demonstration on the Promenade deck where you can make reservations. Diamond members can make reservations in the Concierge lounge. I'd make reservations early if I were you.