I have the following kernel installed: 2.6.18-kanotix-1, which is too old to setup the broadcom card (I think). Does this mean I need to load/compile a new kernel? If so, how do I do this?
For stable bcm43xx (broadcom) connections you need at the very least kernel 184.108.40.206-slh*-2, then
su -c /usr/share/bcm43xx-fwcutter/install_bcm43xx_firmware.sh
because we can't legally distribute the firmware. After doing that (and rebooting into the new kernel) you're ready to configure it just like any other wlan card (take care that netcardconfig can't deal with wpa right now, so that needs to be configured manually --> FAQ).