Get a textbook and read all the sections stated in "What's on the MCAT Exam" document from AAMC. Then, do the Q-pack question by question with solutions, remediating anything you missed or are still weak on (do the odd practice problems at the end of the chapter, for example) until you can do the Q-pack a second time without notes and get most of the answers correct. Then move on to section bank to integrate your new skills into the more complex passages. It took me about 2 weeks to go through all the chemistry with a textbook, and it was definitely high-yield for me because I hadn't had any chemistry in a LONG time... If you need an actual verbal explanation, supplement with Khan videos for complicated topics. And look for friends who can tutor you or help you if you're stuck on something. I found at the local university, they let me come to their open tutoring hours for regular students for free... Good luck!