With that card then you should only need to download the firmware, cut it and configure the card with NetworkManager.
Download this file and put it into a directory somewhere:
Acquire full root rights over your machine with this command in a terminal window:
That's a space and a minus sign after the su. It gives you full root rights over your machine rather than just root rights over your ordinary users environment without it.
Use the cd command to navigate into the directory where you downloaded the above file. Issue the command:
tar xjf broadcom-wl-22.214.171.124.tar.bz2
That unpacks the file archive you downloaded and will create you a new directory where you are working called 'broadcom-wl-126.96.36.199'.
cd into that and then the 'driver' directory within that and use the command:
b43-fwcutter -w /lib/firmware wl_apsta_mimo.o
That cuts the required firmware for your card from the downloaded file and places it in the correct place for the b43 driver to find it.
Check and see if you have NetworkManager showing on the top Gnome Panel to the right in the notification area. If you have ignore the next part.
Go to the "Gnome System Menu - Administration - Services", tick NetworkManager and NetworkMangerDispatcher, make sure they are started and the settings are saved so they start at next boot.
Restart the machine and left clicking on the NetworkManager icon should bring up a list of wireless access points to connect to.
If it doesn't work there are a couple of possible things we may need to alter, mine worked without them though so we'll not complicate things if we don't need to.