This Howto is chapter 20 from Marcel Gagné's new book Moving to Ubuntu Linux reprinted with permission.
Read the chapter here
I also introduced you to the concept of desktop environments and told you that GNOME was the default environment for Ubuntu. There is, however, another very popular desktop environment for Linux called KDE. I highly recommend that you introduce yourself to KDE and that you work with it as well. I make that same recommendation for people already working with KDE, by the way. Try out the GNOME desktop as well. You have a choice with Linux. Why not see what works best for you?