use combination of keys at login screen to switch to console mode
usally in fedora, centos, redhat have "CTRL+ALT+F6" are keys which is used to swtich into console mode, "CTRL"ALT+F7" for move back to GUI.
further go directory into console mode, you need to edit /etc/inittab file
Run the following command to edit the /etc/inittab file:
Press the I key to enter insert mode.
Find the line that includes the text initdefault. Change the numeral 5 to 3.
Type :wq and press the Enter key to save the file and exit the vi text editor.
and than a reboot.
this was started process upto rhel5, fedora older versions and centos5, but from fedora16, CENTOS6, rhel6. they have changed init process with upstart that is module approach to boot the system.
so /etc/inittab file is deprecated, and is now used only for setting up the default runlevel via the initdefault line. Other configuration is done via upstart jobs in the /etc/init directory.
so if you read other documents on internet make sure those are not old.