Submit your resume online through jobs.apple.com.
Good luck.
Since you're 15, not too many places will be looking to hire because of insurance policies. You're really better off working at a clothing store or restaurant (fast food or otherwise). I looked for a job last summer at the age of 17 and not too many places wanted to even give me an application because of my age. I ended up getting a job at the local library where I help run an after-school program for middle schoolers because they really needed a high schooler for the job (it beats being the other high school students who are stuck stocking the shelves).
Nevertheless, I sent in my resume to Apple a month ago after I heard they were readying a Apple Store in our local mall