How to add a CiviCRM extension to Joomla
As you probably know, CiviCRM comes bundled with some extensions, you can add these to your installation from
CiviCRM > Administer > Settings > Extensions, Select the Add New link, then click the download link opposite the extension you want to install.
The CiviCRM Extensions page includes many extensions which aren't bundled with CIviCRM, to install these: