All add-ons installed on your system are available for the System Administrator  in the System Marketplace. Navigate to System Marketplace in the System Admin panel to find all add-ons listed in the system and install those for your system. Installation of add-ons for other users or groups can be handled by users themselves in the Marketplace. To install a system add-on, select the system add-on you want to install and complete the installation procedure. In the System Marketplace, you can also approve add-ons if this option is activated for your system installation 

Installing a system add-on makes the functionality of the add-on available for all users in the system. Users will not be able to uninstall this add-ons. Once an add-on is installed on the system it appears under installed tab in the Marketplace.