Export the publisher file as html.....then open your frontpage web, import that
html file into the web. Publish it.
You can't link directly to the Pub file since this relies on users having
Publisher on their systems.
If publisher can export to PDF format, then this would be a second (more ideal)
solution, convert the pub file to PDF, then in your web page, link to the PDF
file, and publish.
Otherwise, a third option - forget Publisher and redo your newsletter in
Frontpage directly. Using columns and tables, I'm sure you can replicate your
publisher document layout without too much trouble.
Publisher is a desktop publishing (print media) tool not an online tool.