When you sign up for any event and they want to book you, they will send you an email letting you know that it is time to interview. The booking manager's name and number will be in the email where you can then contact them to interview. In the "interview" it will be more of a rundown of what the event will be of and what positions and what shifts they have available so that you can choose on a first-come-first-serve basis. So if you decided you can and the shifts align with your schedule, you will then agree and you will get a confirmation email saying you are booked.

easy. they have to approve you application. not more to that. they don't really try hard in the interview process because all their employees are in a data base so they have a large list to choose from when they need people to word in certain areas.