How sholud my html element <ul> be placed?

HTML-CSS
#1

Tell us what’s happening:
Describe your issue in detail here.
I don’t understand what I should do
what does this mean: Your h2 element should be below the main element’s opening tag and its opening tag should start 6 spaces over from the start of the line.

  **Your code so far**

<html>
<body>
  <h1>CatPhotoApp</h1>
  <main>
<ul>
    <li>
      
      </li>
      <li>

        </li>
        <ul>






  <h2>Cat Photos</h2>
  <!-- TODO: Add link to cat photos -->
  <p>Click here to view more cat photos.</p>

  </main>
</body>
</html>

  **Your browser information:**

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.5060.66 Safari/537.36 Edg/103.0.1264.44

Challenge: Step 6

Link to the challenge:

#2

This challenge is about making your codes more readable by adding spaces to the front of the child elements, so that you can instantly identify the child elements by looking at its indentations.

The <ul></ul> is merely an example with its child elements <li></li> indented, and should not be added to your codes.