Under User | Address book menu you find the window where you create address books.
To create a new folder, click on the 
button and enter the name of the new folder. Another way to do this, is to right click in the tree view and select New | Folder... in the opened context menu.
Create new folder can be carried out in a system global address book if you have Modify system global address book or Own system global address book in you access profile, and in an organisation area specific address book if you have Modify organisation area specific address book or Own organisation area specific address book in your access profile.
The new folder will be placed under the address book/folder selected in the tree structure.
A folder must have a name that is unique in the folder or address book that contains the folder. However, the same name can be used at different levels in the hierarchy. For example, it is permitted to have a folder called Greenkeepers in an address book that is also called Greenkeepers.