Read Chapter 14: "A Simplified Account of Kant's Ethics"
When you are reading Chapter 13, go to the end of the chapter and follow the reading using the four questions at the end of the chapter. Kant's reading is a bit flowery, and the questions will help you follow along much more easily. i really urge you to do this. It will help you on your exam, as well.
There are two versions of the Categorical Imperative that you will need to commit to memory.