Have a look at the past exams to get an idea of what you'll be required to do. Don't worry if you think you can't do the exam, because you aren't supposed to know how just yet (you've got a whole year for that, which is ample time if you have a good teacher), but this gives you an indication of what you'll be working towards.
It's perfectly normal to be anxious and even to lack confidence in your ability at this stage, in fact it's a good thing, it'll give you an incentive to work harder. One thing I really want you to remember though is this: whatever your interpretation of your text is, it is correct. You're a writer yourself, which means that you already have a grasp of how writers accomplish what they set out to accomplish (it may not be a conscious grasp yet). Therefore, you are capable of analytically reading a text for yourself. Don't let others/study guides/anything make you second guess the way you understood it. By all means, let other resources help your analysis, but don't lose your own ideas in the process. The examiners aren't looking for cookie-cutter responses, if you're able to give them something well-argued and genuine then you will do really well.
There are a few examples of lit essays on the forums, and I've posted one of my old ones in the 'notes' section of the site if you're interested in looking at them. They may be more useful later down the track as your course progresses.