microsoft word - How use Heading 1 Style for multiple top-level document entites?

I'm a relative newbie to MS Word, though I have lots of experience with other document-preparation software. As an exercise to help me get used to the Word Way of Thinking, I'm taking an existing document and converting it to Word. I created my own styles, and things seem to look and work fine, but I now see that I'm strongly encouraged to use Word's built-in heading styles, e.g., Heading 1, Heading 2, etc. Setting aside that these names are much less meaningful than e.g, Section and Chapter, I'm having trouble seeing how to apply them to the document I'm working on.

The document has three top-level paragraph styles: Chapter, Appendix, and Unnumbered Chapter. Chapters are numbered 1, 2, 3, etc. Appendices are numbered A, B, C, etc. Unnumbered Chapters are formatted like chapters and appendices, but they're not numbered. Examples include Preface, Acknowledgments, and Index. As I said, each is a level-1 organizational entity, and in fact I've configured Word to assign an outline level of 1 for each of them. But sites like this emphasize how important it is to use the built-in heading styles in Word. How can I do that when I have multiple top-level paragraph styles?

If it matters, I'm using Word 2010.