Just call the 800 number (800-255-2877) and ask them for a Tour of the Dallas Location and they will set it up for you. Tours are run daily at either 10:00am or 1:00pm.
Understand that it is fairly informal and it is a great chance to get your questions answered so be sure and bring some and be ready to ask them. The facility in and of itself is not much to tour... just some offices, a couple of classrooms, the SIM rooms and of course... everybody's favorite part... the planes. You are also welcome to ask any existing students that are on site any questions you may have. Overall I'd say the tour usually lasts about an hour to an hour and a half.