http://www.scitools.com/documents/unix_install.php

Installation
Uncompress and extract the contents of the installation file. For example:
  % gzip -cd Understand-2.6.530-Linux-32bit.tgz | tar xvf -
This will extract Understand. The executable is located in the bin directory.

  % cd bin/linux32
  % ./understand
Add to PATH
The PATH variable should be updated for each user, either in a system-specific location or individually by each user. Add the appropriate bin directory to the path e.g.:

  % export PATH=$PATH:/home/myname/scitools/bin/linux32
Add STIHOME variable for API use
If you're planning on using the C API, add the STIHOME variable to your environment as well. It should point to the directory where Understand is installed. e.g:

  % export STIHOME=/home/myname/scitools