I learned how to develop iOS applications using the Stanford course on iTunes - Developing iOS 7 apps for iPhone and iPad.
Although this course will soon be out of date (with the introduction of Swift and iOS 8), its a good introduction to programming for iOS and a good introduction to Xcode which can take a bit of getting used to.
My advice when learning to develop for iOS would be to practice and then practice some more. Don't expect your first application to be successful overnight.
If you want to learn how to develop apps, pick a simple app from the app store and then try to write it yourself. You don't have to submit your app for publishing, its just practice on writing apps.
The more apps you write the better you'll get.
Whilst you're learning, look at the apps that you like in the app store and ask yourself why you like them. Is it because of the way they look, or the way they do things? How are they different from the way you would have designed and developed the application.
You need to learn, not only by practicing, but also by seeing what other developers are doing.
You'll get immense satisfaction when you've written an application that you're proud of. So just take the plunge and good luck