Adel, it looks that you see the network
Your wlan0 interface should be up by default (double check using ifconfig
wlan0)
Once you know that wlan0 is up by default
(/etc/sysconfig/network-scripts/wlan0.cfg) Try:
iwconfig wlan0 mode Managed
iwconfig wlan0 essid globalnet
dhclient wlan0
You should receive an ip address proven that you or your sysadmin have
configured your dhcp to assign addresses to any device on the network.
This should connect you. After that you might need to share that connection
with other devices but that's another story. If I want to connect my phone
I don't go through my PC but directly to my wireless router. I would advice
you to use network-manager it's pretty straightforward and you don't need
to be root.