How to upgrade your joomla to latest version
Check to make sure your hosting allows you to install Joomla! 3.3. The minimum required PHP version is now 5.3.10, but it is highly recommended that servers are update to the latest version of PHP 5.4 (or 5.5) for best performance, security and compatibility.
Click on the “Install the Update” button and allow the update to run
When it has completed you may need to refresh your screen or empty your browser cache to adjust for template CSS changes.
Note: Joomla! will notify you on your administrator home page (control panel) when an update is needed, but it will not do the update for you. You need to press the button to start the update.
Recommended Steps and actions:
It is recommended that you follow these steps when updating a production site:
- Back up your site before upgrading to a new version. That way, if something goes wrong during the upgrade process, you can easily restore your site to the earlier version.
- Review the release notes for the new version to be familiar with what was changed.
- Update using one of the recommended methods outlined in this document. These methods install the new program files, delete unneeded old program files, and update the database as needed for the new Joomla version.
- Clear your browser cache and check that the update was successful, using the steps outlined in the Checking Site tab.
The above post gives you step by step process to upgrade joomla to latest version.