Two paths diverged in a woods...
There are two different directions you can go here.
One is a top-down, academic, computer science approach.
The second is a bottom-up, practical, tutorial approach.
In the academic approach, you learn about such things as computers, object orientation, binary, Cocoa design patterns, encapsulation, and many other topics.
In the tutorial approach, you learn from modifying working small applications and seeing what happens. You learn about Interface Builder, connecting your code to what the user sees, making the dots on the screen do X instead of Y, having something happen when you tap a button, and many other things.
I'd strongly recommend the tutorial approach for you. Take a look at rwenderlich.com and pick a tutorial you're interested in. Google iOS tutorial or osx tutorial or iphone prgramming tutorial or iOS game tutorial or whatever interests you. Have fun!