In the left "Section" navigation, click on "Biography". The main window of the page will scroll down to that portion of the listing. The Biography section is one large text field that can accept basic formatting. You will need to click into the Biography section to see the text formatting tool. It will appear at the very top of the as shown in this screenshot below.
As with all sections in people listings, a proper heading will automatically appear on the page above the text you enter into it. If the information that you're adding is long and complex enough to need headings within it, please use a level three (H3) heading when breaking information up into distinct blocks. Headings can be accessed from the drop down menu showing "Paragraph" below.