Connect an external drive (e.g. Flash drive) to the tablet's USB port (located on the right-edge).
Utilize File Explorer to transfer data between the external drive and the tablet.
For Windows 8: If File Explorer doesn't launch automatically, swipe up from the Start screen, tap Desktop then tap the Folder icon (located in the lower-left).
For Windows 10: If File Explorer doesn't launch automatically, from the Windows desktop, navigate: Start menu icon > File Explorer.
For further assistance with File Explorer, refer to Microsoft's support article How to Work with Files and Folders.