iPad drill down menu

I'm trying to build a program which when it opens, has 4 large buttons, each button will take the user down into a sub menu, this sub menu will contain a list of items which is selected the user can view more about and then return开发者_开发百科 to the list of items. The user can then return back to the main screen.

Which order do I go about doing this? I'm stuck logically at how i'm going to design it?

Sounds like a good several reads through the Documentation may help answer a lot of your questions. Specifically the View Controller Programming Guide and Navigation Controller Programming Guide should be very helpful in giving you a good idea of both how to begin structuring your application and implementing it.