Editing "Read Only files"

I am a Newbie to the Linux world and am trying to set up Knoppix 6.4.3 on my Acer Aspire 3000 Laptop.
Everything works OK with the exception of my wireless system which seems to point to the Broadcom Bcm 4318 wireless adapter and it appears that the fix is to edit the configuration file, broadcom-sta-common.conf, located at /etc/modprobe.d and to comment out the 'blacklist b43' statement in the file. I have arrived at that point and am unable to edit the file as it is 'Read Only' and I have been unable to write to it.
How does one change the permissions to overcome this? My Knoppix has been installed to a USB 4GB flash drive via the procedure in Preferences, "Install KNOPPIX to flash disk".

sudo leafpad /etc/modprobe.d/broadcom-sta-common.conf

or sudo pcmanfm and navigate to that folder
or when you open the filemanager(pcmanfm) in tools you can open curent folder as root

now it isn't read only anymore

Many thanks. That worked just as you said it would.