This exam will primarily cover Unit 3, the Biological Basis of Behavior. There will be some questions from Units 1 and 2 as well, so you need to review everything. The exam will be a combination of multiple choice questions and a free response question.
I suggest doing the multiple choice practice tests in the study guide to help you decide what to spend the most time studying.
If you start to study asap and distribute your studying over as many days as possible you will learn and remember more than if you just cram for a couple of hours the night before the test. Then again cramming for a couple of hours is way better than not studying at all.
Good luck.... although luck doesn't really have anything to do with it.