Begin by downloading PreviewPlus from : SOMEWHERE
As prerequisits you will also require FFMPEG, LAME and OpenOffice. On Ubuntu/Debian you can install these from the package manager. On RedHat/Fedora you may have to install them by hand depending what repositories you have available.
Instructions assume eprints is installed at /opt/eprints3
Extract the tarball into your local archive directory:
cd /opt/eprints3/archives/ARCHIVEID tar xvzf PreviewPlus.VERSION.tgz