Intermediate Beginners/Converting an Existing Website to Joomla
From Joomla! Documentation
< J1.5:Intermediate Beginners
The "J1.5" namespace is an archived namespace. This page contains information for a Joomla! version which is no longer supported. It exists only as a historical reference, it will not be improved and its content may be incomplete and/or contain broken links.
Check out the Converting an existing website to a Joomla! website guide for great step by step instructions.