Apple is made up of many different departments, and Retail is just one of them. It seems like you did some programming courses and expressed interest in it—Apple has a software development team, but it's not like you could work at a retail location selling iPhones and hope to become a software engineer by just climbing a "the ladder." You have to actually apply for those relevant positions to get into the right department and go from there. Also, almost every programmer at Apple in the U.S. is located in Cupertino or Santa Clara in California (they're nearby), so you would have to be willing to relocate.
Here's some advice:
- Focus on school and get good marks in your classes. Graduate with at least a B.S. in CompSci or similar STEM degree, and if you really love it or want to explore a more academic realm of this area, get an M.S..
- Participate in clubs around campus for programming. Get involved. I'd also suggest working for a smaller local company that is relevant to what you want to be doing later in life to get job experience.
- Once you get the degree, apply at Apple for a number of positions that you would be interested in. Believe me, once you go through college you will have a much better idea. I'd also apply at Google, Facebook, etc for the more known companies if working at huge tech corps your cup of tea, and even lesser-known companies in Silicon Valley (if that's where you want to be) to improve your odds of landing these jobs.
Apple is a great company to work for, but you're not the first person to want to work at Apple. All of those positions are well sought after. Expect there to be a lot of competition for each position, and getting a degree in these environments is a must-have if you want to work for these larger corporations, but it's only a prerequisite. The real way to differentiate yourself from the rest is the existing experience from previous jobs, clubs, etc and the drive to want the job. I think that if you really do posses the drive then you will get the job, or an equivalent from another business out there.
Good luck!