When connecting to the Fresco with a micro-usb cable, the unit will display a drive and files of the Fresco unit.
The drive may not show up immediately, depending on hardware revision, you may need to restart the Fresco (Menu -> Setup -> Restart) while the micro usb cable is connected to your computer and the Fresco unit.
On newer Fresco hardware, plugging the in micro usb cable to computer and to the Fresco unit, will cause the station to restart, this is intentional, and the drive will be available to access.
In either case, a drive will appear named FRESCO, while on the FCS7 unit itself, will display a message indicating it is ready and once done, can be unplugged to restart.
Also, check activity with micro usb cable, is the usb indicating it is doing something (virus scanning, loading driver, etc). These events may cause the Fresco to take a longer period of time before the drive becomes available.
Fresco will power cycle and enter the "USB Connected Mode" when USB power is detected. It is possible that either the cable, USB port (or USB hub if applicable) don't allow for USB data traffic. Verify the cable, and USB port function correctly. If using a USB hub, verify Fresco isn't connected to a USB charging port only.