Dowload it from this page-
Select 32-bit or 64bit which ever your computer architecture you have--
Then depending on what commandline utility your distribution uses: use that to install the flash player-
Sorry I am not familuar with the distro Knoppix. If (Knoppix) it's Ubuntu or Debian based you would want a tar.gz package and use apt-get.
If Red Hat based you would want a rpm package and use YUM to install-