Check the nps.gov website for the admission hours that day.
Go to the lodge on 15th Street, which opens one half-hour before the monument tours begin. The site suggests visitors be at the lodge at 7 a.m. during the peak season of April through September. All tickets are given out a first-come, first served basis.
Tell the ticketing agent how many tickets you would like. One person can pick up as many as six tickets.