Adding a UINavigationController
Up to this point, you have used Interface Builder for your interface needs. Interface Builder is fantastic for designing individual screens of your interface, but when it comes to linking those screens together, doing it in code is much more convenient. So you are going to build your navigation controller entirely in code.
As discussed earlier, you need to create a UINavigationController instance in the applicationDidFinishLaunching: method of the application delegate. For CelebriTweets, the CelebriTweetsAppDelegate is the class you need to modify. This class was created automatically when you used the Window-based Application template to create the project.
The first step ...