Untar the package file to your GIMP directory:

  $  cd ~/.gimp-1.2/
  $  gunzip -c /path/to/pmosaic-0.1.tar.gz | tar xf - 

The software will be extracted to the 'plug-ins' directory.

Start GIMP. You should see two new options on the Xtns/Perl-Fu menu of the
main toolbox. 

  photomean

and

  pmosaic

Although these are provided in the GIMP's menu system it is recommended for
performance reasons that they be run from the command-line or in batch. See
the in-line documentation for full details.

Before using the photomosaic software please run at least the pmosaic.t and
photomean.t tests to verify correct installation and functionality. These can
be found in the t/ directory from wherever you untarred the package.

  $  cd plug-ins/t
  $  perl ./photomean.t
  $  perl ./pmosaic.t

If everything passes you are all set! 

For best results, the more photos in your library the better. I recommend
around 4000 at an absolute minimum. 7-8000 should be adequate.

If you create any really nice photomosaics with this software email the author
and I'll consider adding them to the pmosaic home page at
http://thebigmachine.org/gimp/pmosaic/

Happy Mosaicking!