Support for the Joomla! CMS can be found on several places. The best place to start would be the official Help Site. Here you can help yourself to the information that is regularly published and updated as Joomla! develops. There is much more to come too!
Of course you should not forget the Help System of the CMS itself. On the topmenu in the Back-end Control panel you find the Help button which will provide you with lots of explanation on features.
Another great place would of course be the Forum . On the Joomla! Forum you can find help and support from Community members as well as from Joomla! Core members and Working Group members. The forum contains a lot of information, FAQ's, just about anything you are looking for in terms of support.