The official MCAT registration materials include a syllabus that spells out the subject matter tested in detail. The essay section consists of two timed half-hour essays. In each essay you are asked to interpret an open-ended ambiguous statement. The physical sciences test covers inorganic chemistry and physics. Nearly all students require at least two months of regular review to cover all the necessary material.
Many students require longer.
You can then spend the final 2 or 3 months reviewing and solidifying the information you have already learned. For example, if you read your textbooks heavily in class, then review your textbooks. If you used study sheets or notecards in your classes, then review those. Most pre-medical students find they don't have the time for MCAT review unless they make a concerted effort to make the time. No matter what you do, take lots of timed practice tests.