Changing the Font Size of an Element problems

Tell us what’s happening:
I’m confused on how to correctly change the font size of an element, i’m extremely new at programming and would just like to see if someone can properly explain it to me and throw out some examples.

Your code so far

  .red-text {
    color: red;
  h1 {font-size: 16px;}

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

<p class="red-text">Kitty ipsum dolor sit amet, shed everywhere shed everywhere stretching attack your ankles chase the red dot, hairball run catnip eat the grass sniff.</p>

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (X11; CrOS x86_64 9000.82.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36.

Link to the challenge:

you are setting the font size for h1 and then using h2.