To add a new add-on, go to Settings / Add-ons, select an add-on and click on the "Details" button for more information. To install it, click on the "Install" button in the dialog box that pops up.

Most add-ons can only be installed in one copy, but there are also add-ons that can be installed in multiple copies. In the latter case, the system will ask you for the name of the instance you want to install before installing: you can enter any name that will identify this instance of the add-on.

(If no add-on is installed, the "Add-ons" menu item will not appear!)

After deleting an add-on, all data that was in the add-on will be irreversibly deleted. Some add-ons are free, others are paid. In the case of a paid add-on, please contact the add-on developer for details.