Changing front page

I do not understand how to change anything on the front page. In the Dashboard there is an “Edit your front page” link. When I click on it there is an Edit Page on the top and an area below the Add Media button for evidently adding/changing things on the front page. Within that area there are is an image pointing to one of my media images.

If I add anything text below the image, nothing changes whatsoever on the front page.

I am using the WP Opulus theme.