There are three stages, the first being an online application, which stands out as they ask for no resume. Then there are two rounds of group interviews.
In the first we're asked to roleplay together, working in teams, for some sort of high stress fictional situation (like an invasion by pirates). After that we're asked to present a story we've been provided before-hand from memory. Make sure to monitor how loud you are, although you'll likely be interviewing with 10 other people, you may wish to be loud enough to be heard by 20 in a non-acoustic friendly environment. If you forget a line, move on to the next. They're looking for accuracy of the information contained within, storytelling capability, and fluidity of voice. Avoid awkward pauses at all costs. As for the story itself, it will be told on location, which means you'll be walking for about an hour. You can add colour to it, but don't embellish, add miscellaneous information, fake facts or guesses or jokes. If in doubt, don't do it.
The second interview will follow a similar course to the first. Group improv and then a walkabout, presenting in an outdoor location. You'll be asked to play an improv game or two with a partner this time for the first half. In the second, you will have been provided a list of facts for a specific location beforehand, and be asked to give an introduction to the location, followed by quick trivia (i.e. you asking questions, your fellow applicants replying). This is a bit more freeform, and has a limit of 5 minutes, being timed. Again, charisma, no pauses, and loudness are all things to consider.
I'm aware I'm making this sound hard, but its a very welcoming atmosphere, mistakes can happen. Remember to be positive with your fellow applicants, and with the interviewers and you'll be fine.