The code you are referring to is for embedding Discourse comments onto a page on another site - so you could use Discourse as the commenting engine.
What I understood from your original post is that you were simply trying to display the Latest or Category pages on that other site. In that case, simply add the URL of that page in the iFrame wizard and the Discourse site should display. Have you tried that?
However, whether this works or not is probably a function of the Wix widget and site and not Discourse itself.