You need to follow the proceedures in: "iPhone Developer Program – Standard Program Portal User Guide for iPhone". You can download developer guides from the program portal.

There are about 14 pages of proceedures that you must follow from the section "Building your Application with Xcode for Distribution"

These proceedures tell you how to set up your build and then how to chesk/twest the binary and also how to create a zip file. It's the zip file that you upload to AppStore.