Hopefully I am understanding your question....
Stanza needs a xml db file as would be generated here:
https://www.mobileread.com/forums/showthread.php?t=62332 in order to know where to get the book from. You can only import files into the stanza program through the stanza program, not through safari.
The easiest way to get them into Stanza is to download them directly from fictionwise. On the first page of the Stanza program, go to Online catalog > Fictionwise > My bookshelf. You will be asked to sign in (you can save you password) and any multiformat book you own will be available for download, automatically as epub.
Hope that helps.
Beau