Hey thehomiebilly, I'd go ahead and start making your art school journey thread and post in the art school section where all the cool peeps will maybe help you there.
I haven't taken the course, I assume its every tool used to manipulate color and value. Using the lasso tool to single out sections of the image like body, lake, beach, sky etc. On each selection you make use Ctrl-B Adjusting colors, ctrl-U adjusting color, ctrl-L to adjust level values. Adding layers of color mode, multiply mode etc and painting on color or.
Main thing when you mix colors, is checking if its:
A:Darker or Lighter
B:Warmer or Colder
C:Brighter or Duller (saturated)
So in digital painting its kind of the same thing. But making broad sweeping changes.