The Dharma Guide: Setup additional add-ons
You can expand your XBMC-Experience by installing Add-Ons/Plugins. Since XBMC Dharma we have a repository installed from which we can choose additional Add-ons/Plugins. You can find this sub- section on the home-screen. Hit the "Add-On"-Section in XBMC and choose "Get Add-ons" – browse and install what you like.
You have the option to install extended repositories which will enhance the available Add-Ons for your experience. To find repositories just check this site in the XBMC-Wiki: 3rd party add-on repositories
Download the Zip-File, open up the "Settings" -> "Add-Ons"-Menu and choose the option "Install from Zip-File". From the dialog-window pick the downloaded zip-file. After the installation you can choose Add-Ons from this repository. If you do not see any Add-Ons after you added the Repository, navigate to the Repository ("Add-Ons" -> "Get Add-ons"); bring up the context-menu and hit "Refresh Repository" in order to load available entries to the database.