If there is a way to connect to the Internet, you can install the following packages in order to use wireless connections.
Open the Software Center and search&find&install these packages:
b43-fwcutter
firmware-b43-installer
or you can install these packages with a terminal command(Short cut:Ctrl+Alt+T):
sudo apt-get install b43-fwcutter firmware-b43-installer
If your pc haven't a another internet connection, you can download driver packages from the following urls.
http://packages.ubuntu.com/quantal/b43-fwcutter
http://packages.ubuntu.com/quantal/firmware-b43-installer
Please, be careful of packages architecture(The packages architecture you will choose must be same as your Ubuntu architecture.)
After this operation reboot your system and connect a wireless network.