Click on one of the options:
a) Section Headings - these are the main titles that appear in a sales quote at the beginning of a section
b) Heading 1, 2, 3, 4 - these heading styles are using in text content blocks, you can select text and make that text a heading, this is the same as in all word processing applications such as MS Word or Pages.
c) Body - this is the styling for "normal" text in a text content block
Select an option and adjust the available settings for font face, size and colour, as shown in the example below.