Thank you for your post.
If you launch FileMaker Pro on the server and open the file, pull down the File menu and select "Sharing -> Instant Web Publishing...". Turn on Instant Web Publishing, and in the bottom left of that dialog box, select the file(s) you want to share, and then on the right side select access to "All Users". Then, external users can launch a Browser and enter:
This will launch the Instant Web Publishing page and the users can select which file they want to access.
If you need clarification for any of the above steps, please let me know.