I infer from the context of your questions that you are actually running Knoppix 5.1.1 (?), in which case the following will be available to you:-
1. Kmenu -> System -> More Applications -> File Manager - Super User Mode
2. Navigate in file manager to /etc/apt
3. Click on the sources.list file to open it with Kwrite
4. Add to sources.list file the statement
Code:
deb http://www.debian-multimedia.org etch main
BTW "etch" is an alias (or vice-versa) for what is now "stable" Debian. (I prefer to use named designations as it avoids ambiguity with older system sources.list files where "stable" used to be "sarge" - which is now "oldstable" . )
BTW for these codec files you might be able to use lenny(=testing) or sid(=unstable) with Knoppix 5.1.1 libraries, but I haven't tried mixing them so no guarantees .
5. Save the amended /etc/apt/sources.list file.
6. From a root-privileged console invoke
Code:
apt-get update
(I forgot to mention this first time )
then
Code:
apt-get install  liblame0 lame
and it should install for you .