Headings are important to screen readers and therefore accessibility. The page heading is automatically the Heading 1 on each page. After that headings must follow proper levels e.g. H2, H3, H3, H3, H2, H3, H4, H2...
To use a heading on a page, use a Rich text widget in a Section
Highlight the text that is to be a heading
In the visual editor toolbar, click on More Paragraph dropdown
Use the Paragraph Format drop down to select the heading level appropriate.