How do I write files to a CD

When i try to write files it tells me that the filesystem is read only. I have a cd-rw drive and the disk I am trying to use is cd-rw. I really need to save some stuff to back it up and be able to transfer it.
It depends on what type of burner you have. For ATAPI, use burncd. For SCSI and USB, use cdrecord. Before burning you should generate an ISO-file. And: Do not mount the cd when burning. Here is how I do it on my system (ATAPI):

# mkisofs -o cd.iso -r <files>
# burncd -e -f /dev/acd0 -s max data cd.iso fixate

For more info, check the handbook:

Good luck!
For GUI environment a nice stuff is K3B program (sysutils/k3b) - dependency from KDE libs
(read /usr/ports/sysutils/k3b/pkg-message-7 for correct installation)
or Gnomebaker (sysutils/gnomebaker) - depend from GTK/Gnome. PS: Both of them is "backend" for cdrecord