1) Find out the wireless device name.

#iw dev

2) check wireless device status up or down

#ip link show wlan0

3) scan wireless networks

#iw wlan0 scan

Now to configure and connect wireless without GUI we will require package wpa_supplicant-0.7.3-9.el6.i686

4) Create a configuration file

#wpa_passphrase >> /etc/wpa_supplicant/wpa_supplicant.conf

5) To start the device through command line

#wpa_supplicant -B -D wext -i wlan0 -c /etc/wpa_supplicant/wpa_supplicant.conf

where -B means run wpa_supplicant in the background.
-D specifies the wireless driver. wext is the generic driver.
-c specifies the path for the configuration file.

put above command in /etc/rc.local so that after booting it will automatically connect to wireless device.