When you want to use USB as a location you have to make settings for USB first. You can make the settings in WebTools Express.
Choose [Print from and scan to], when you want to enable print from and scan to USB.
Choose [Print from only], when you want to enable print from USB only.
Choose [Scan to only], when you want to enable scan to USB only.
Choose [None], when you want to disable the USB functionality.
When you enable USB and insert a USB key on the user panel, the external USB location can be used via the user panel and in WebTools Express.
When you disable USB, USB cannot be used as an external location.