What do I need to change to enable me to move a file from my hard drive to my usb drive?
GNU/Linux, of which openELEC is a form, attaches external storage as subdirectories of the root filesystem -- usually in
/mnt, although they can go anywhere.
I'm actually not a openELEC user so I cannot provide you with specifics, but if you browse through the
/mnt directory while the drives are attached you should be able to figure that part out. The next aspect has to do with permissions; as a particular user you may be allowed to view a directory but not write things to it.
If you know where the second drive is mounted and you are just using this on a home LAN (i.e., don't have to get too paranoid), you can make the directory world writable with:
chmod a+w /mnt/foobar
/mnt/foobar is the subdirectory. This won't persist across reboots though.