If all this discussion of notebooks and sections is alarming, and you're not a natural filer, do not panic. You won't have to search through OneNote, looking for the section you want, in each meeting you attend. Instead, you can just start taking notes, then sort them out later. There's a section called Unfiled Notes that's designed just for this scenario. Take notes in there, and then organize them when you have time. The Unfiled Notes section is where your screen clips and side notes go, too.
Keep in mind that OneNote always opens at the same place where you closed it. So whenever you open OneNote, you'll be exactly where you stopped last time.