First, find out if the final exam is cumulative, or only covers the material since the midterm.
Next, ask the instructor if there will be any study guide or any tips on what to focus on.
Depending on the scope of the exam, review all the material. Hopefully, you have been keeping all with the work and will only need to review and not re-learn everything. Once you’ve reviewed it all, then focus in on the parts that you have the most trouble remembering. If there is something you don’t understand, try to meet with teacher outside of class to go over it and make sure you understand.
That’s it. It’s just a big test so you prepare for it in basically the same way you prepare for any other test. Again, this process will be much easier if you have been keeping up with the work and not letting things slide.
Good luck!