I recently took the HESI and got 100% on the A/P by using the pocket prep app. I would say that generally if you can do the pocket prep q's, then you should be fine on the real section. Some of the pocket prep q's were seemingly more in depth than the actual exam. I can tell you that the majority of the questions were not too specific- such as knowing the general joint types+ examples (elbow, shoulder etc), bones (I wouldn't worry about the specific bones in the wrist or anything). Also the General nervous system (brain parts, CNS, PNS, parasympathetic vs sympathetic effect on body). Outside of the app's material, i would also study bone ossification basics (crash course has a good video), body cavities+what is in them, muscle contraction basics, and also arteries (if you know the body region names then it is not difficult). Also, I would review the pigmentation of skin basics (I went back to my textbook for this). When I took the A/P section, the questions felt similarly formatted. They were not the same questions from the app, but they felt familiar in terms of how they were worded and answer choices. The A/P II questions were very simple (unlike some of the app q's) so I wouldn't worry about those if you did well in your class.
Hope that helped a bit! Good luck on your test