When you enter Folder Settings, you will be on the General tab.
You can click the Folder Opens and Folder Closes dates to edit them.
You can edit the dates directly or click the triangle to change the date via the date picker.
You can edit the times directly.
Click the Permissions tab to view and edit the permissions. If you are not going to edit the permissions, click Save.
If the folder is a sub-folder, the parent folder(s) must also be open in order for students to access the sub-folder.