Adding storyboard to existing project

Those exact steps (I am using XCode 4.5 and iOS 6.0 ):

1. Add new storyboard to the project by File->New->File...->Userinterface->storyboard
2. Go to project summary and select MainStoryboard and select the storyboard name you just created.
3. From AppDelegate.m file in method didFinishLaunchingWithOptions, comment everything except last statement which returns YES.

That is all. Now you should see your Initial view as you launch the project.

For XCode 6 and iOS8 beta2:

1. Create a Storyboard file (let's call it Main.storyboard). Pick an iPhone or iPad for device type.
2. In the blank Main.storyboard file, drag a UIViewController from the object library.
3. If the storyboard is intended to be used as a universal storyboard, then switch to the File Inspector (in the Utilities section on the right), and check mark "Use Size Classes".
4. Select the View Controller in the storyboard and switch to the Identity Inspector (in the Utilities section on the right), and type in the "Class" field the name of your View Controller.
5. Find the file "info.plist" in the "Supporting Files" folder on the left in the Navigator section.
6. Add a row by clicking on the '+' sign to the right of the "information property list" key.
7. Select "Main storyboard file base name" key, and type the name of your storyboard file, in the "Value" field (in this case it will be called "Main")
8. In AppDelegate.m/AppDelegate.swift, in the method/func "application:didFinishLaunchingWithOptions:"remove all code except "return YES" (for Objective-C), or "return true" for Swift.

I've found answer on my own question. It's very simple: I should open storyboard, select view controller (it's visual representation on storyboard), then go to identity inspector and replace class UIViewController to your controller class