Hierarchy Side-Bar (Need Help Constructing)

So, I'm completely new to Objective-C (I have a little experience with Java and am currently taking a C++ course to try and understand the C language better in general) and I'm trying to figure out how to teach myself the things I need to learn. I'm hoping that you guys can at least point me in the right direction for tutorials or books or give what I'm trying to do a name so that I can refine my searches.

This is a program called Spyder, and I'd like for the program I'm currently working on to have a sidebar very similar to the one here. There need to be delimiting categories, like Library and Network, and then inside each one there needs to be collapsable collections of... Whatever fits in that category.

Once I figure out how to even put that in the window on the Interface Builder, however, I still don't know how to saturate it with things from my program (for example, I wouldn't know how to make it add all of the queued blog posts that you've saved to a collapsable menu for posts). But I'd assume that I can at least find that in my ebooks that I've already got on hand.