• Be assumption that you have HTML as example and the question here `How to target to HTML element by using pseudo class`?
<div class="wpb_wrapper">
<div>...</div>
<p>...</p>
</div>
• With CSS3, you can follow here:
.wpb_wrapper p:first-of-type { ... }
or
.wpb_wrapper p:nth-of-type(1) { ... }
Keyword: CSS selectors, HTML element, pseudo-class, targeting element.