Download the latest Joomla patch version - here I’m going to upgrade Joomla version 1.0.9 to 1.0.10. The latest reeases of Joomla is always avaible at the Joomla development sourceforge system.

Download the latest file to some path in your system, here I have downloaded it into the Joomla directory.

cd site
tar xvzf Joomla_1.0.1_to_1.0.10-Stable-Patch_Package.tar.gz
chown -R username:groupname *

And you are done - Always remember to do a working backup before upgrade - just in case.