It's okay to be nervous, but remember, the whole point of Prep is to help you figure out plot, characters, settings, an outline, etc. You're not competing with anyone (unless you choose to participate in the weekly contests), and everything is geared toward getting your thoughts together before writing in November. Just take your time, do the exercises, and keep them to yourself if need be - no one else ever has to see any part of it if you don't want them to.