Missing X11R6 libraries

I finally figured out how to painfully setup OpenGL with GLU, GLUT, and GLUI, but now I'm lost as I need to link several X11R6 libraries which don't exist on my computer. :(

I installed Ubuntu using the instructions found on TeachWeb. I'm wondering if there's a sudo get-apt command or something like that that will easily install all my missing libraries.

All in all, my /usr/X11R6/lib directory is empty, and me wants to fill it and I know you guys and gals are the Linux gurus. Thanks in advance!!

Cheers,
Tom