I don´t remember well now but you only need to download the tar.gz, extract it, and place the libflashplayer.so inside /usr/lib/mozilla/plugins or if you also use firefox inside /usr/lib/firefox/plugins In other live cds it is in /usr/lib/flashplugin/... I don´t remember now if there was an /usr/lib/iceweasel, I am not using knoppix now and I don´t use iceweasel, I normally download firefox and execute it manually, so I was copying libflashplayer.so inside /usr/lib/firefox/plugins and restart.