Besides controlling sharing at the individual Document or File level, you can also set sharing at the Folder level. Whenever you set Folder sharing, all Documents in that Folder (and any subsequently newly created Documents) are automatically given the Folder’s Share Settings.
To set Folder-level sharing
Set Sharing on Folder Sets
To set the sharing on a Folder Set, you'll first need to make sure that you navigate to the folder set that you want to share in the Navigator, and then click on the "Show" link to show all of your folder set on the right-hand side of the screen.
Learn more about Folders and Folder Sets.