1.) When you extract the "gesource" folder, make sure another "gesource" folder isn't inside the *initial* "gesource" folder.
 - When you extract the "gesource", opening it should show a "maps" and "scripts" folder.
 - Whichever "gesource" folder that shows the "maps" and "scripts" folders immediately on opening it, is the one that should be used in Step 2.

2.) Put the "gesource" folder in this directory:
 - C:\Program Files (x86)\Steam\steamapps\SourceMods (IF YOU'RE ON A 64-bit SYSTEM)
 - C:\Program Files\Steam\steamapps\SourceMods (IF YOU'RE ON A 32-bit SYSTEM)

(Or wherever else you know you installed Steam)

3.) If asked to overwrite anything, do it.

 ~Zippy