You need an extension called jSecure Authentication for this recipe, which you can download from the Joomla! extensions directory at http://extensions.joomla.org/extensions/access-a-security/site-security/5809:
1. Install the extension through the Extensions | Install/Uninstall option in your Joomla! administrator panel. In particular, you'll need to ensure that the
\plugins\systemdirectories have the necessary permissions set to allow Joomla! to copy files to and from them. Next, you need to navigate to Extensions | Plugin Manager.
3. Once installed and configured, log out of your...