First, thanks for the replies!
I believe they're all unzipped, but that's a good next thing for me to check.
And yes, I have imported them, using the arrow-down beside the 'add books' button, and selecting 'add books from directories, including sub-directories (multiple books per directory; assumes every ebook file is a different book).'
I understand about the DOC formats, too, but these are showing up as LIT, when I filter by format, then seem to not be able to actually locate the LIT files themselves.