To help make Microsoft Word documents accessible, use heading styles (located in the style gallery) to add headings and subheadings to structure your content. The heading levels should follow the structure of your document's outline. Appropriate use of heading levels will help those using screen readers to interpret how the page is organized, allowing for quick navigation to different content areas.
To find available heading styles, on thetab of the ribbon, go to the "Styles" group:
To create a heading in Microsoft Word:
If you've expanded the styles gallery and still don't see the heading level you need, you may need to tell Word to show all styles. To do this:
All heading levels will now be visible in the "Styles" panel, and will be accessible from the styles gallery once you've used them in your document.