On the bottom panel there are the "Add folder" button, the "Delete folder" button and the "Apply settings" button.
The "Add folder" button is used to add any folder to the list.
The "Delete folder" button is used to remove the selected folder from the list.
The "Apply settings" button is used to save modifications in the list. All folders (files inside that folders) in the list will be protected from deletion. You can protect as local as network folders and files.