iOS Twitterfon landscape?

I understand that this App is no longer open source but I have the last version that was available for open source and I would like to know how to make it to where you can rotate the App to landscape? I want to slowly try to make a personal App. Would this be a lot of code? When Im in IB it rotates and everything but when ever you build it into the iPhone sim it does not. So as I said before it has to be something that has to do with coding right? I'm very new to Programming period, Thanks! 