Well it depends on what you actually want it to do.
Having a popup come out when you click a button is easy enough.
Making a list of items is easy enough. You just have to click a button to make a list of items inside a popup.

I suggest you take the examples in the NGUI project and fiddle around with them and see if you can make the scroll list, for instance, dynamically. Trying to mess with the existing stuff is a good way to learn.
I'm not sure there is really a guide for something like this, although I stumbled on a simple menu tutorial here
http://www.youtube.com/watch?v=kdL318_J6_E that might help.
I hope that helps.