Front end link to invoke editor with Category and Tags set?

My user who is a "Contributor" is browsing an archive of "Products" postings.

I want to add a link to the bottom of the archive that says "add new"

When the user clicks the link they will go into the Administrative back-end and be presented with an edit post screen that has the Category and Tags for the post correctly set.

* How can I construct such a link?