Davis Auditorium is on the campus level of the CEPSR/Shapiro building (technically this is the 4th floor since the Columbia campus is on a hill; the 1st floor on this part of the campus is the level of 120th street).
The layout of the campus may be found on the interactive campus map, Section D and CEPSR/Shapiro is clearly marked.
Since the first two days of the Agents School take place on a weekend, bear in mind that the only access onto the Columbia campus will be through entrances at or below 116th Street. All gates above/north of 116th are locked.
Registration will take place by the entrance to Davis for the first two days of the school. From Monday morning, the registration desk will move to Alfred Lerner Hall where the main AAMAS conference will be located.