There are two ways to retrieve a list of posts for a weblog: one is via the feed, and one is via the protocol. The link to the Atom feed is often linked to or referenced from the homepage of the weblog, or page you are visiting. Those references are often found embedded in the HTML you are looking at and are not visible to the user unless you view the source of the web page. Somewhere towards the beginning of the HTML file you will find a "link relation" that looks something like this:

<link rel="alternate" type="application/atom+xml" title="My Atom Feed" href="http://feeds.feedburner.com/SixApartProfessionalNetwork">