You need to install the "sablotron" package.

You need to install docbook-xsl-1.68.1p0.tgz

You use the sablotron command sabcmd and give it the style sheet and then the xml file to transform

An example would be sabcmd /usr/local/share/xsl/docbook/html/docbook.xsl /home/dude/howto/example.xml > example.html