How to add a sidebar?

Hi,

I'm trying to understand how to add a sidebar in a singular view rendering the layout between header and footer. I can't find anything in the documentation or in the support forums on it.
I see a fieldtype sidebar, but that adds a sidebar to an individual post... I don't understand the use of that as well.

So I'm quite in the dark, hope you can share some light on this subject.

Thanks.