how to make a class in html

.myclass {
  border:1px solid black;
  background-color: #d2d2d2;
  height:20px;
  width:60px;
}
/*If you give this class to a div in html, it will get the styles you gave
to that class. You can add multiple classes to a div, and multiple divs
can get that class. */
/* I hope I helped! */

<h1 class="write a name">H1 content</h1>

<p class="ClassExample">ClassExample!!</p>

<p class="ThisIsAClassName">HI</p>

<ul class="legend">
    <li><span class="greendot"></span>Text</li><br></br>
    <li><span class="yellowdot"></span>Text</li><br></br>
    <li><span class="reddot"></span>Text</li><br></br>
    <li><span class="blackdot"></span>Text</li><br></br>
</ul>

<!-- in the head element -->
<style> h1 { color:blue; } </style>

<!-- in the body element -->
<h1> text in blue because all "h1" element is in blue </h1>