The add folder functionality allows you to create a structure into which you can upload images and other files so you can use them with your themes.
To add a file to the root folder:
Navigate to Control Panel Dashboard > System Administration > Site Administration > Site Content > Site Files.
Click Create New Folder.
A Create New Folder dialog box appears.
Enter the folder name and click Save. The folder displays in the workspace.
You can Upload a site file to the new folder by browsing to it and clicking Upload. To view the list of files in a folder, click the folder name.