How do I add a class `the_content();`?

```
<div class="csoporszoveg">
    <h3 class="csoporcim"><?php
        if ($settings['enable_link']) {
            echo '<a href="' . get_permalink($post) . '">';
        }

        the_title();

        if ($settings['enable_link']) {
            echo '</a>';
        }
        ?>
    </h3>
    <?php } ?>  
      <?php
        if ( $content_source == 'excerpt' ) {
            the_excerpt();
        } else {
            the_content();
        }
      ?> 
</div>

```