This is both a tutorial and an informational page about the Apple Podcast ChapterTool utility and Podcast Chapters in general. This article is a part of the iTunes tips entry. The tutorial section will show you how to add chapters, chapter images and chapter links to your podcasts. It is relatively technical, so hopefully a GUI based chapter tutorial program will come out soon, but in the meantime this is the best and only way to accomplish this task. Link.
HOW TO PodcastChapterTool