Headers are important to both draw attention to certain text by increasing the size and boldness as well as to improve SEO. To setup a header, you must create or edit an existing post or page.
Note: If you do not see this drop-down, you may have a plugin or theme that has changed how this appears and will need to consult documentation for that plugin or theme.
Once you have saved your changes, you have added headers to your WordPress page or post.