The best way to learn AutoCAD is to:
A) Look online, Try and find some AutoCAD guides, many schools offer them so you should be able to find something.
B) fiddle, Play around with it, try different things. It may seem hard at first but you should get the hang of it.
C) If you are trying to learn how to use it for school, why not ask a drafting teacher, or someone with engineering knowledge.