A menu consists of a numbered sequence of choices. Each choice has the form
* {manual(Tag)} Subject
If you are running Prolog without Emacs, you can select a menu choice by typing
| ?- manual(Tag).
where Tag is exactly as shown in the menu. Tags are in general of the form Chapter-Section-Subsection-... where Chapter, Section, and Subsection are abbreviations of a section in the printed manual.
Under Emacs: you will find that a special mode is entered when you are looking at a menu. See ref-olh-hlp, for more information.