Lecture #19 looked at resolution.
Notes are available in four formats:
The lecture covers much the same material as Chapters 14 and 16 of the textbook. So you need to go through these.
Note that Chapter 16 goes into a lot of detail about unification. While you should understand what unification involves I don't think there is any need for you to try to memorise this material; just read it through and make sure you understand what is going on..