Headings in a document are not meant to assist formatting, but to provide information on the structural hierarchy of a document. It is important to use them appropriately to convey document structure, since some users skim through a document by navigating its headings.
How to select the heading type in WordPress
The title of your post or page should, in theory, be an H1 heading – it is important for you to check this before you proceed. Do this by looking at the source code for your site, and finding the title of the post or page.
First select the text you are going to convert into a heading.
In WordPress, the button to expand the tools and reveal the headings select field is called “Kitchen Sink”. You can click it or just use the keyboard shortcut “Alt + Shift + Z”.
Then you can select headings from a drop down select field, which usually has as default value “Paragraph”.