After downloading, enter into the directory where you have saved instantjchem-VERSION.zip then uncompress the zip file.
Gives the home directory of your Java by editing instantjchem/etc/instantjchem.conf. (See Howto change IJC's Java.)
You can start applications by script, which you can find in the instantjchem/bin directory.
Requires Sun’s Java 1.5 (or later). You can download it from Oracle’s Java web site or contact your OS manufacturer.
You need an expander which can handle zip extension.