If you wish to uninstall an extension on your Joomla! site, then follow these simple steps:

1. Select "Extensions" and then "Install / Uninstall" from the drop-down menu
2. Select the type of extension you wish to uninstall. You will have the choice between Components, Modules, Plugins, Languages and Templates.
3. Find the extension you wish to uninstall and check the checkbox to the left of the extension title.
4. In the upper-right corner of the screen, press "Uninstall"

It's as simple as that. If Joomla! can't uninstall the extension, you will be prompted with an error message. If this happens, it's most likely to be caused by the extension. As extensions are developed by third-party volunteers, you will have to try to get support from the developers of the specific extension.