Is there any way to create an ebook with chapters directly from .rtf?

I'm trying to convert a light novel in e-book, but would like a way to make the Calibre or another program allow me set the chapters or identify text in bold as new chapters.

I tried to add html elements in the texts and did not work. I have low knowleddge about this area, so if possible I'd like something pretty easy. Something that allow me to jump directly for a chapter using Kindle chapter menu.

Sorry for anything, used google translator.