Download iso.tar.Z (about 6 MB) into that directory.
Unpack the files using the command:
zcat iso.tar.Z | tar -xf -
Add an environment variable ISODATA which contains the full path to the isobyu directory. For example, if the full path is /usr/local/common/isobyu/, then the command in c shell would be:
setenv ISODATA /usr/local/common/isobyu/
Everything should be ready to run. Try running ISOTROPY by entering the command, iso.