You can download the update directly on yoru device through the Apple App Store or by using the link which follows:
Apple Store version 2.4 has the following features and improvements
- Buy new gift cards and email them to friends and family right from the app. These gift cards are easily integrated with the new Passbook app (U.S. only, iOS 6 required).
- Ask Siri to help you find prices and shop for Apple products. (Siri-enabled device required.)