When you use TournamentSR's "File" menu to "Open..." or "Save as...", the folder selection drop down list doesn't include your USB flash drive.  To use the flash drive, change the folder selection to "Macintosh HD" and then double click on "Volumes".  You will see the name of your USB flash drive in the resulting list.  Double click on the USB flash drive name to locate or save the tournament file there.