So, for example, if you wanted to add SEO Scoop's feed to your site, you would click on the little orange XML button at the bottom of the home page. (Other sites may show different graphics, often it will be an orange RSS button). This will take you to the raw feed code. You can ignore the code itself. Instead, copy the URL of the feed that appears in your address bar (in this case, http://www.seo-scoop.com/rss/seo-scoop-rssfeed.xml). Now go to the AmeriVault RSS parser page at http://www.amerivault.com/news/syndication/amvrss.php and paste the SEO Scoop RSS URL into the form. Configure your colors and options, and you can see the output of what your feed would look like when you hit the Go! button.
A simple search in Google for "your subject matter" + "RSS" will probably result in quite a few options for content you can add to your site.