How to Install an Extension with Joomla! 1.6

Thanks to the constantly growing community of Joomla! users and developers, there are literally thousands of extensions that you can download and install to extend the functionality of your Joomla! site. With Joomla! 1.6, installing new extensions has never been easier:

1. Locate and download an extension from one any trusted online source.

   
   



2. Choose Extensions→Extensions Manager from any back end page. Extension Manager opens.

   
   



3. In the Upload Package File section, click the Choose File button to browse to and select the extension you want to install to your Joomla! site.

   
   



4. Click the Upload File & Install button.

   
   

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Source:http://www.dummies.com/how-to/content/how-to-install-an-extension-with-joomla-16.html