Exposer is joomla-article-based, which means Exposer can only display things that are already on your site. At best, this content are articles that are categorized or tagged with TAGS. So in order for Exposer to display something on your site, we need to do some "pre-work" on an empty installation (which is necessary anyway).

In short, categories are like chapters in a book or... Sections in a folder (a real folder, with paper, hence the name... not the folders on your desktop :-) )
To learn more about categories in Joomla... yes you know how the sentence ends -> Link

Create your first category

Navigate in the Joomla! backend to the menu entry Content --> Categories, you will see the following view:

Note: If you have installed the demo content during the Joomla! installation or with your template you have already listed some categories here, but this is not a problem, we simply ignore them rigorously

We now simply create a new category using the button "New" in the upper left corner:

There is not much to do here, just enter a title (hello joomla!) and some Description text. Take care that the Status on the right side of the screen is set to Published and the Access to Public.

Finally, we click on Save & Close, the list of categories should now have been extended by our new category:

And that's it in the next step we create some demo articles.