Help on "Use an ID Attribute to Style an Element"?

I don’t know what to do next, I added “#cat-photo-element {background-color: green;}” inside my style element already but I don’t know what to do from there to make the background of my form green

Your code so far

<link href="https://fonts.googleapis.com/css?family=Lobster" rel="stylesheet" type="text/css">
<style>
  .red-text {
    color: red;
  }

  h2 {
    font-family: Lobster, Monospace;
  }

  p {
    font-size: 16px;
    font-family: Monospace;
  }

  .thick-green-border {
    border-color: green;
    border-width: 10px;
    border-style: solid;
    border-radius: 50%;
  }

  .smaller-image {
    width: 100px;
  }

  .silver-background {
    background-color: silver;
  }
  
  #cat-photo-element {
    background-color: green;
  }
</style>

<h2 class="red-text">CatPhotoApp</h2>

<p>Click here for <a href="#">cat photos</a>.</p>

<a href="#"><img class="smaller-image thick-green-border" alt="A cute orange cat lying on its back. " src="https://bit.ly/fcc-relaxing-cat"></a>

<div class="silver-background">
  <p>Things cats love:</p>
  <ul>
    <li>cat nip</li>
    <li>laser pointers</li>
    <li>lasagna</li>
  </ul>
  <p>Top 3 things cats hate:</p>
  <ol>
    <li>flea treatment</li>
    <li>thunder</li>
    <li>other cats</li>
  </ol>
</div>

<form action="/submit-cat-photo" id="cat-photo-form">
  <label><input type="radio" name="indoor-outdoor" checked> Indoor</label>
  <label><input type="radio" name="indoor-outdoor"> Outdoor</label>
  <label><input type="checkbox" name="personality" checked> Loving</label>
  <label><input type="checkbox" name="personality"> Lazy</label>
  <label><input type="checkbox" name="personality"> Energetic</label>
  <input type="text" placeholder="cat photo URL" required>
  <button type="submit">Submit</button>
</form>

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_4) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/11.1 Safari/605.1.15.

Link to the challenge:
https://www.freecodecamp.org/challenges/use-an-id-attribute-to-style-an-element

Again you should understand the instruction properly first . First the challenge shows you on how to change background color using id attributes but then it tells you change the background color using form element itself instead of the it’s id attribute and thats where you did wrong you used id instead of the form element :

#cat-photo-element {
background-color: green;
}

It should be :

form{
    background-color:green;
  }

The id for the form is “cat-photo-form” . So you need to write:
#cat-photo-form{
background-color:green;
}