Click Filelist in the left hand menu. This accesses the File structure where pictures and files are kept for easy access while working in TYPO3. (img. 3.1.1)
To create a new folder, right-click on an existing folder and select "New". (img. 3.1.2)
By using the drop down (1) you can create up to 10 folders at a time. Type in the titles of the folders (2). When you are done click "Create folders". The new folders will appear in the Filelist. (img. 3.1.3)