All you need to do to upgrade a Joomla website is download the Joomla upgrade package to your local computer, extract it and upload the files to your web hosting account, replacing all existing Joomla files.
If everything goes smoothly, your Joomla will be upgraded. However, we would recommend you to back up your Joomla files before making the upgrade.
More information on how to upgrade your Joomla can be found in our tutorial here.
If you wish to migrate your Joomla 1.0.x to 1.5, please refer to our migration tutorial for information on how to perform this upgrade.
To provide an easy way for updating Joomla, the SiteGround team has created the jAutoUpdate component. It can be used to automatically update a Joomla application to the latest 1.5 version available with a single mouse click.
Joomla is a powerful software that is easy to work with once you have the right host to support you. Before you lose any more time with the wrong host, check out the hostlantern Joomla hosting offer.