When you run K3b for the first time, you may find K3b informing you that no optical writer drivers have been found, meaning you will not be able to write to any optical discs. There is no need to panic as K3b will open a configuration window which will help you get various tools used by K3b up and running. This includes viewing the user group that owns those applications. You shouldn't need to change this as K3b will apply the correct permissions on external programs itself. These programs are generally cdrecord, growisofs and cdrdao. If preferred, one can tell K3b to use the burning user group and point it to the optical drive. Below is an image of the configuration window where these settings are possible.