When I installed Ubuntu Server 12.04, I selected the ethernet adapter because I will use that most often; however, I would like to use wifi sometimes as well.

This is how far I've gotten with this problem.

lspci 
02:00.0 Network Controller: Intel Corporation PRO/Wireless 5100 AGN [Shiloh] Network Connection

iwconfig
wlan0  IEEE a/b/g/n  BSSID=off/any  Mode=Managed  Access Point=Not-Associated TX-Power=off  Retry Long Limit:7  RTS thr:off  Fragment thr:off  Power Management:off

I tried to do iwconfig wlan0 up but that doesn't work either. The error message said something along the lines of rfkill but I'm not connected to the Internet to download that particular program.

Any help here would be great