To create a new folder, you navigate to the document
library where you want to create the folder and then to the folder in
the document library where you want the new folder to be (if you don’t
want it under the root of the document library). Then switch to the
Documents ribbon and click on the New Folder button in the New section.
A New Folder dialog appears, asking for the name for the new folder.
Enter the name and click Save to create the folder.
The New Folder button is unavailable if any of the following conditions are true:
The document library is configured not to allow creating folders.
You do not have permissions to create items in the document library.
The current view is configured to display as a flat view.
Folders are handled as list
items in the document library. This means that if a library requires
approval, the folder is not visible to other users until it is
published and approved.