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.