Use Headings for section titles and sub sections. This lets you style all the section headings the same very easily. It’s also used for creating an automatic table of contents later on. The easiest way to change a style is to set a line to a specific heading (see the dropdown in the toolbar labeled “Normal Text”. Then, change the style of that line, and then right click the line and select “Update Heading to match”. Then boom all your other headings will match that style. You can go to Format->Paragraph Styles to tweak your headings even more, to give them borders or background colors.