This is the "Help Text" tab from "Project | Documentation Options". There are two tabs here, "Heading and Topic Title Settings" and "Header/Footer".
Heading and Topic Title Settings
You can choose between using the Title as the heading or to use the Nonscroll Help Text. You can also control the look of the Heading and Topic titles. If you check the "Add Page Break" option it will place your Heading or Topic on a new page.
Header / Footer
If you click in the Header or Footer section you can type in text and format it, in the same way as you can with help text. This text will appear in the header and footer of all pages except the Front and Back Cover.
You cannot simply refer to page numbers as fields, as in MS Word. In Fast-Help you need to specify the page number separately. In the middle of this tab, you need to type in the reserved word [PAGE_NO]. Fast-Help checks for this during compile. You can specify whether you want it to appear in the Header or the Footer, and by using the alignment settings on the bottom right, you can choose its position.