Replacing UINavigationController With A UIViewController in MainWindows.xib

[anumamin]

I am a newbie to iPhone app development. I want to make a simple app using view-based template which will have a main menu(home screen) linking to different modules of the app. Modules will themselves be made up of either UINavigationController or UITabController.First I just wanted to create and bug a module, so I took a NavigationController inMainWndows.xib(appDelegate) and stacked(linked) many ViewControllers to it.Now I need to have main menu at start of app, where I have placed NavigationController. I am now confused what to do? I have got solution in my mind that place this NavigationController in new xib file and a mainMenuViewController in MainWindow.xib file and access navigation module as a modal. So my Question is that if my approach is right? How will I access this modal controller to push viewcontrollers onto it? Or is there other alternate for what I want..?I hope my Question is clear... Any suggestion or link is appreciable. I am using xcode 4.​