Apple has published a App Development Tutorial to teach you how to write apps using Swift for the iPhone.
If you have an iPad, you can also download the Swift Playgrounds app to get started learning Swift interactively.
There are other sites around the net with dev tutorials, such as Ray Wenderlich's iOS Tutorials.
BooksIf you prefer learning from a book, there are plenty to choose from! Check out the most popular iOS Programming and Swift Programming books on Amazon.
Big Nerd Ranch offers excellent iOS and Swift bootcamps which take you from novice to iPhone developer in just a few days. Class tuition includes room and board for the week. I took their first iPhone bootcamp in 2008; it was excellent and I highly recommend it.
There are also a number of Conferences for iPhone Developers.
Read the Apple Docco.
There's a ton of information, documentation and examples on the Apple site. Here are some starting points:
Visit Apple's iOS Developer Center for more documentation.
The best way to learn is by doing. Figure out what you want your app to do, and start building it. You can refer to Apple's sample code for ideas. If you get stuck, ask for help on Apple's iPhone Developer Forums. Another great resource for programming questions (and answers) is Stack Overflow. And don't forget about Google; you can search for the thing you're trying to code, or the bug you're trying to debug, and turn up lots of useful info.