Initially your site does not have any content, and that is where the fun begins. Use the thin black administration menu across the top of the page to accomplish many of the tasks needed to get your site up and running in no time.
Select Content -> Add from the administration menu (remember that little black bar at the top of the page?) to get started. You can create a variety of content, but to start out you may want to create a few simple Articles or import items from an RSS Feed
Select Configuration from the administration menu to change various configuration options and settings on your site.
Select People -> Users from the administration menu to add new users or change user roles and permissions (please note tabs on the far right).
Select Help from the administration menu to learn more about what you can do with your site.
Don't forget to look for more resources and documentation at the OpenPublish website.