Rich text fields have a formatting bar above the text field. Use the formatting bar to format your text. In order to ensure that your content is accessible, it is important that you use the Format menu on the toolbar to make your content accessible.
From the University’s Accessibility website:
Heading tags are intended to convey a document's structure and aid navigation for screen reader and screen magnification users. Heading tags should never be used to control font characteristics. Failure to use heading tags for their intended purpose or in a logical and consistent manner may negatively impact comprehension and navigation for some users. Use a level 1 heading <h1> to indicate the title, topic, or purpose of each page. Repeat all or part of the level 1 heading in the <title> element. Use level 2 headings <h2> to indicate main sections of the document. Use level 3 headings <h3> to indicate sub-sections. Use level 4 <h4>, level 5 <h5>, and level 6 <h6> headings to indicate sub-sub-sections.
For more information on making your content accessible, please refer to the accessibility website: Core Skills for Headings