Once ready, go to the Joomla! Update component. Click on options and change the setting to Short Term Support. Save. You should be notified of the availability of Joomla 3.x. Click the button to install. Clear your browser’s cache to make sure you see the latest changes. That’s it!
Finally, double check and make sure that everything is working properly.
Note: On some hosts you may need to use alternative update methods such as using the extensions installer.