Download and install the latest OS X drivers from the Apple web site
Verify the Airport hardware is setup correctlyOpen the Airport application or Internet Connection Application.
Ideally you should see, that the configuration is "AirPort", that the AirPort power is "on", that the AirPort Network is listed as "UGA" or "Wireless Network".
If "AirPort" is not selected in the configuration you will need to select it. If the AirPort power is turned off, you need only click "Turn AirPort On" to activate the card. If the network is not set to "UGA" you will need to change it to "UGA".
Open your System Preferences application. It is listed in the pull down menu under the Apple Menu.

In the System Preferences application select the Network icon (on the top row).

All network configuration is done within the Network preferences window.
Select the TCIP/IP tab to configure TCP/IP settings.

Select the AirPort tab (This tab only appears for Wireless ports using Apple's AirPort card. If you have a third-party wireless card, a tab with a different name may appear, and you will need to consult your vendor's documentation to learn how to configure your wireless card.).

To preserve any changes you have made click on the "Save" button ("Apply Now" in Mac OS 10.1), then close the network window and your system preferences window.