I agree with what others have said. The amount you need to study greatly depends on your background. I graduated with a degree in Nutrition Science, which includes almost the exact material you’ll find with ACSM. It’s very science-based and focuses a lot on human anatomy, the physics of exercise, and the science behind nutrition. My previous background in that material helped out a lot, but I still read the “Resources for the Personal Trainer” book cover-to-cover and attended the online workshops (really helpful!). If you already have a good knowledge of kinesiology and physics, that may be all you need. Otherwise read the book, attend the workshops, and work on the practice exams. It’s not an easy exam, so you want to be sure to be prepared and give yourself enough time to absorb the material.
Best of luck!