I had a quick look. You need, using ndiswrapper, the Windows driver.
Brows to the medium where you got it (the Windows installer CD i.a. or download the Windows driver)
Then, when in the folder with driver content, open a konsole.
Become root (su <enter>, password <enter>)
Type: ndiswrapper -i bcmwl6.inf <enter> (Yes, bcmwl6 is what I found is the driver .inf flie)
My guess: That will do it!