Originally Posted by: gmixstudiosok I understood everything in circle of 5ths lesson right up until lesson 4 when it washed right over my head

Most of that concerns how neo-classical guitarists use "slices" of the circle of 5ths in their chord progressions. Look at the circle of 5ths image and notice that the progression D-G-C-F, etc. is a part of the circle.

Essentially, they accomplish this by means of secondary dominant chords. Basically, every chord is the fifth or V chord of the next chord! Look here for more:

http://www.guitartricks.com/tutorial.php?input=495

Lesson 7 is about secondary dominants. But go through the whole tutorial in order to learn and gain the context of the concept.

Ask more questions as necessary!