For most applications, a structure something like this would be appropriate:
Introduction: A basic description of what the application does and any noteworthy features, etc..
KApp: Task-based description of the most common uses of the application.
Program reference: Description of all of the features of the application. This could include a menu reference, but might also include command line options, syntax description, etc., if they are appropriate to the application.
This chapter should list all of the application windows and their menubar and toolbar commands for easy reference. Also include any keys that have a special function but have no equivalent in the menus or toolbars. This may not be necessary for small apps or apps with no tool or menu bars. Link to default menuitems in the Fundamentals.
Frequently Asked Questions: List the most common questions and problems that users have with the application, and their solutions. “How do I ...?”-type questions are especially appropriate.
Credits and License: A list of those who contributed to the documentation, and a link to the GNU Free Documentation License, under which all KDE documentation is licensed.
This chapter is required for all KDE documents, and must have at least the two license links (one for the document, and one for the application)
You will find a template document with these sections in template docbooks in the KDE Git repository.