If you have an AirPort Express connected to your stereo or powered speakers, you can play iTunes music using AirTunes.
Connect your stereo or powered speakers to your AirPort Express using the mini-jack on the top of your AirPort Express, and then plug your AirPort Express into a wall outlet.
Open AirPort Utility, located in the Utilities folder in the Applications folder on a computer using Mac OS, and in Start > All Programs > AirPort on a Windows computer.
Click Music in the toolbar, and then select the Enable AirTunes checkbox.
Enter an iTunes speaker name and password. This is the name displayed in the pop-up menu at the bottom of the iTunes window.
If you’re setting up your AirPort Express for the first time, choose Base Station > Assist Me, and then follow the onscreen instructions.
After your AirPort Express is connected and properly set up, open iTunes and choose your AirPort Express from the pop-up menu at the bottom of the iTunes window.