In order to configure Joomla to work by more than one domain follow these steps:

1. Park the additional domains to your account. This can be done from cPanel, Parked domains;

2. Open Joomla's configuration.php file and make this change:

$mosConfig_live_site = 'http://'.$_SERVER['HTTP_HOST'];

In case your Joomla is in a subdirectory you have to specify the name of the subdirectory:

$mosConfig_live_site = 'http://'.$_SERVER['HTTP_HOST'].'/directoryname';

Note to substitute directoryname with the the directory name in which Joomla resides.