How to get an airport card worked?

[sowhat59]

I've had a Macpro 2008 quadcore 2.8 and just purchased an airport card to join the wireless internet world.
I successfully installed it myslef but can't get online.
I purchased this one.
http://www.amazon.com/Apple-MB363Z-...TW/ref=sr_1_31?ie=UTF8&qid=1330156885&sr=8-31

It didn't look necessary but I downloaded
http://www.amazon.com/Apple-MB363Z-...TW/ref=sr_1_31?ie=UTF8&qid=1330156885&sr=8-31

and when I click on dmg file, it says my computer is not compatible with this enabler.

I'm guessing I need some sort of enabler or software to get online?
My computer got a full wireless signal and detects most of wifi around my house. The airport card itself works fine. I just can't get online.

Another thing I tried: in "Network Utility," there's a "network interface (en2)" menu under info tab. If I choose that one, it shows "model: Wireless Network Adapter (802.11 a/b/g/n). "
But when I close the window, it doesn't stay with that menu and go back to en1, which doesn't detect anything.



Can anybody tell me how I can fix this problem?

Thank you!