Each course is different - some have prerequisites, and some don't. Take a look at your specific course’s recommended prerequisites on the course description page. If you do not meet a particular prerequisite, you may still take the course. Remember there is no penalty for not completing a course!
All required academic materials will be provided during the course, within your browser. Some courses may list additional resources on their course description pages. For supplemental reading material during a course, post a question in the course discussion forum to ask your classmates and course staff for suggestions.
And, of course, be sure to check out DemoX to get a better sense of the edX platform and how courses work.
Note: In the edX app, sections that have prerequisites are not visible in the course outline until after you complete the prerequisite.