You can delete subfolders in your personal folders. For other folders you need to have the required permissions.
How to delete a folder:
Warning: If you delete a folder, all subfolders and objects in this folder will also be deleted. Deleted subfolders and objects cannot be restored.
Note: To delete a folder, you need to have administrative rights for this folder.
In the folder tree, select the folder that you want to delete.
Confirm that you want to delete the folder.