changing to cdrom in repositories

[Cheatah 0#@!^]

how to include cdrom in my "Manage repositories" page? so that i can
install from cdrom in my kubuntu 6.06. i cant see the cdrom option in
the page.i tried to add it by modifying the page /../sources.lst in a
terminal. i added it in this way  "deb-src /media/cdrom main
restricted" and then enabled it from the "Manage repositories" page.
but that shows error while i try to install from cdrom. i tried to put
the above line at many places in the sources.lst, but that doesnt
work. where should i actually place it??
please help.