Do you have signal strength from the Airport?
Here is how you can check...
Look in the menu bar...
Do you have any 'waves'?
If this is an empty triangle 
you have no reception, meaning you aren't in range of an airport
Or your Airport card has been turned OFF
Go up to the empty triangle and select the airport named SAD6-Wireless Network
Now your computer should be able to "talk" to the airport and on to the rest of the network.
(You should be able to read your mail and reach web pages.)