how to edit class in css code example

Example 1: how to make a class in html

<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>

Example 2: css calss

.ThisIsAClassName{
  font-family: sans-serif;
}