So In order to get the iPad version working, follow these steps:
First go to your target settings, scroll down to "Deployment Info", and change it from iPhone to Universal
Next you will need to create a new Storyboard file. On the bar at the top go File>New>File and this thing should pop up: After you have selected iOS>User Interface>Storyboard as shown above, click next and it will ask iPhone or iPad. After selecting iPad, the new file will be ready to map your interface for iPad. However, you need to make sure the app uses it. So go back to your target settings and scroll back down to "Deployment Info" and switch to iPad:
Set the "Main Interface" option to the name of your new storyboard file.
As for preparing for iPhone 5, that part can get a bit annoying. I find that the additional space is too small for any major additions but too large to be ignored easily. How you deal with it will vary greatly depending on what you app does. From what you described, with app icons like the iPhone screen, you will probably want to have an additional row of icons, just like the iOS. To do this, you can either manage it programatically or you may want to have seperate storyboards for iPhone 4 vs iPhone 5. If you want the separate storyboards, this question will have your solution.