There are certain folders that exist which contain essential files, but should not be displayed. Typically, these folders are called "images", "blocks", "pdf" and "doc" and are already hidden. To hide other folders or pages, do the following:
Select the folder or page you wish to hide. (In this instance, the folder is "Picnic"). Click the edit tab.
If editing a page, make sure the tab selected within Edit is "System".
Submit and then publish the folder above the updated page/folder.