With the phone interview they mostly ask you basic questions just to get general info, and they also ask about symptoms/disorders and how they interfere with your functioning and ability to work...so all you really have to do is be straightforward about that stuff.

Beyond that after that they should send paper-work with more in depth questions you have to fill out and send back, then depending on if they feel they have enough evidence or not they might schedule you an appointment with a doctor to get their opinion.