The package can be downloaded from several places, including http://josefsson.org/shishi/releases/. The latest version is stored in a file, e.g., shishi-0.0.42.tar.gz where the 0.0.42 indicate the highest version number.
The package is then extracted, configured and built like many other packages that use Autoconf. For detailed information on configuring and building it, refer to the INSTALL file that is part of the distribution archive.
Here is an example terminal session that download, configure, build and install the package. You will need a few basic tools, such as sh, make and cc.
$ wget -q http://josefsson.org/shishi/releases/shishi-0.0.4.tar.gz $ tar xfz shishi-0.0.4.tar.gz $ cd shishi-0.0.4/ $ ./configure ... $ make ... $ make install ...
After this you should be prepared to continue with the user, administration or programming manual, depending on how you want to use Shishi.