This page will walk you through the installation of Wifi drivers — assuming that it didn't work out of the box.
One area where Linux is still lagging behind Windows is in wireless networking — a.k.a. “wifi.” There are a number of wireless networking cards which will work out of the box, with Ubuntu — you can find a list here — but there are many, many more cards that won't. And, in the Linux world, it's not as easy to get your card working as simply popping in a CD with your drivers, like it is in Windows.
However, there is no need to fear; even if your wireless card isn't supported by Ubuntu out of the box, you can use your Windows drivers, in Ubuntu, using a tool called the NDIS Wrapper.
Before you can get started, you'll have to make sure that you can connect to the internet somewhow. Hopefully, you have a wired connection in addition to your wireless connection — otherwise, you're out of luck for wireless networking!
Your first step should to be to make sure that your system is up to date, using the System->Administration->Update Manager application.
Once this is done, you can go to System->Administration->Restricted Drivers Manager, and enable the driver for your wireless card.
There may already be an icon showing up in your Notification Area, saying that you have restricted drivers you can enable. If so, you can click that, which is the same as going to System->Administration->Restricted Drivers Manager.
When you select the driver you want to enable, you will have to confirm that you really want to install it. Once you do, Ubuntu will download and install the required packages from the internet.
You will next be asked where to get the “firmware.” I choose “from the internet” for my system.
And this is it. At this point, you've got your wireless drivers installed, and you can start using your wireless connection. Unplug your network cable, and you'll notice that your network indicator, in the Notification Area, will show that you have no connection. Click it, and it will present a list of available wireless networks.
Chances are you'll have to configure your wireless network, by entering in the appropriate security information. You'll have to speak to the person who set up your wireless network for these settings.