dont worry about it too much. i did mine almost a month ago. i wasnt really nervous. umm it was really casual..we were all waiting outside woolies for the interview and i started a conversation with this chick who's my age. sat next to her when we got in. it felt really casual, and the interviewers or whatever were really nice..we only had two of them even though on the email it said there'd be others aswell..
first thing is the introducing thing. easier than you'd expect. you just ask the person next to you questions about their life and whatever you want, then present it to the group.
second is the proritising activity. very easy.
and last is the test, which we didnt do because they lost the sheets haha