[SOLVED] Add Widget to Single Page to display RSS feed

I am using Atahualpa 3.7.3 with WordPress 3.3.1 for a client's site, let's call it site 1. She wants to display all the posts from one category on another of her WordPress sites (let's call it site 2) on the "Posts Page" on site 1. I found a plugin that will display a category specific RSS feed in a widget but cannot figure out if it is possible to add this widget to the center area on the page that I've designated as the WordPress "Posts page" (in WP Settings > Reading).

So I want this widget to display only on this "Posts page"... I've tried Juggledad's thread from a few years ago on how to add a widget after 2nd or 5th post but editing index.php as instructed did affect this "Posts page."

I think my client is asking for a lot but I would like to look smart enough to actually produce the results she wants if it is possible. I appreciate your help, as always.