Notice how the h1 element has both an opening <h1> tag and a closing </h1> tag, with text in between them. All of that makes up the entire element. And the opening and closing tags need to have the same name (h1) in this case.
So you want to create a new element, an h2 element, below the h1 element and add the text Cat Photos to it. This means creating both the opening and closing tags for the h2 element and then putting the text inside of them.