Using the page headings will not only make it easy to navigate the information you wish to present to the visitor but it is also used by screen readers as navigation through the information. Screen readers use the heading tags as markers allowing a visually impaired person to navigate through the information on a page using a screen reader.

Headings Tool
The headings tool is located in the toolbar in the top row, the sixth icon over. 

Headings Tile 
Left Justification
Along with headings, it is important to leave all text titles and headings left justified. Adding an indent or spacing can cause problems with screen readers. Leave the indents and center/right justifications for print media. This goes for electronic documents also