Your DropBox account contains folders taken from your computer and stores music, videos and documents for sharing or synchronizing to linked computers. Rather than have all of your files in one folder, Dropbox allows you to create subfolders within folders to organize your data for easy access and storage. Newly created folders are automatically saved in your account, and are available to all authorized users of your DropBox account.
Add Folder from Compuer
Click "Finder" on your Macintosh's desktop or "Windows Explorer" on your PC's taskbar, and double-click the DropBox folder to view the main folder.
Double-click the folder you wish to open, and click "File" at the top of your computer's menu. Click "New Folder" to create a new folder within the currently opened folder.
Create a name for the sub-folder, and press "Enter" on your keyboard to save the folder's name. Drag and drop items from your computer or DropBox account to the newly created folder. Users who have access to the shared folder will see the new folder upon logging in to DropBox from their account.
Add Folder from Website
Log in to your DropBox account through the site's main page (see Resources).
Click the "Files" tab at the top of the browser window, and double-click the folder you want to configure.
Click "New Folder" and enter the folder's name in the text field. Click "Create" to save the folder. Click and drag files to the new folder to automatically add them to the subfolder.