I'm moving your question to the InDesign EPUB forum, the best place for EPUB questions.
Are you trying to create a reflowable EPUB or a fixed layout EPUB? What version of InDesign are you using? These are essential questions to answering your question.
It sounds like you've had no instruction about creating EPUB from InDesign. I highly recommend two resources:
(1) A book called Digital Publishing in InDesign CC by Sandee Cohen and Diane Burns:
(2) Anne-Marie Concepcion's videos on EPUB at Lynda.com. You can get a free 10 days viewing videos at Lynda.com.
It's really hard to learn what direction to do with EPUB and how to do it without some instruction.
I am trying to do a reflowable ePub, since the fixed layout isn't yet supported by all devices and publishing platforms.
I have Adobe InDesign CS6.
Thank you for your links. But it would also be nice to know, what to look for from the instructions after learning the basics, considering my original question.
The main point is that you can have only one text flow in reflowable EPUB.
An EPUB already comes with a Navigational TOC which does much of what you're trying to do.
You could also do those elements as sidebar text frames which are anchored into the main flow of text.
Both of the sources I gave you explain that in more detail.
Thank you Steve! I'll keep on looking the videos and instructions.