That screen is for the AUTO ADD folder to prevent unwanted files being processed (if that folder has other uses)
Look at the second tab (Adding Actions): Bottom button
When I started with Calibre, I imported only a selected file type from BAEN CD's.
Using the command prompt: (for more command help: Type Help xcopy)
(the
/s say do sub directories also)
Code:
xcopy <the base path>*.epub <auto add folder path or tempfolder> /s