This article explains how to install a GUI desktop (Gnome) on a Redhat or CentOS system and have the system boot to that GUI on startup.
yum -y groupinstall "Desktop" "Desktop Platform" "X Window System" "Fonts"
To have Gnome start on boot, you will need to edit the file “/etc/inittab” and replace the following:
id:3:initdefault:
With this:
id:5:initdefault:
You can change to the GUI without rebooting by entering the following:
init 5