After you have created a news item you can select a checkbox to mark that article as the site's "Lead Story".

There can be only one "Lead Story" per site. Child sites can have their own independent (different) Lead Story.

If you set up an area of your site as a separate section and the editor of that area wants to use the Lead Story feature to easily nominate one article for publication in a prime location, then you will need to set up that area as it's own site. This isn't difficult within SocialFX as the system has been designed to help you to set up child sites.