Headings are very important part of the content that can easily be used in WordPress Editor. These not only divide the content on your website page for better visualizations, but also helps increase the site SEO. Because it tells search engines like google the important points of the content on your site.
See following video demonstration to use headings in WordPress Editor.
There are 6 heading styles in HTML starting from H1 being the biggest size and most important part of the content.
In WordPress Editor you can easily add headings in your content using WordPress editor. Jus select the text in the editor, and select relevant heading from the first by clicking on dropdown menu in the first row of editor tool that is by default set to paragraph.