go to http://www.digitas.com/careers/internships for all the details on applying to the program:

what's in it for the interns: positions available across capabilities; a chance to work and live in one of our 6 US locations including Atlanta, Boston, Chicago, Connecticut, Detroit, and New York; a 10-week program commitment starting June 7–August 13; 100% dedicated to their capability supporting real client work; a fun day/outing to give them an opportunity to get intimate with their new city and peers; a summer project which is their chance to pitch their work to us; and, finally, weekly training sessions to give them exposure to other capabilities