Earlier this month, Joomla announced the availability of Joomla 2.5.2. Calling it a security release, it emphasised on the goal to continue to provide regular and frequent updates to the community. You can download the latest version of Joomla here. Alternatively, you can update from an earlier version of Joomla by downloading the package here.
Joomla 2.5.2 security update available
In order to update to Joomla 2.5.2, you would have to follow the basic principles with any upgrade. First on the list is backup! For a detailed tutorial on backing up your Joomla site, read this piece by OSTraining.
Once you have backed up your site content, login to your admin panel. Depending up on the version of Joomla you are using, you will find a flashing icon indicating an update is available. Simply click on the icon, select the package and click on update and you're done. It's that simple.