I wonder wether you have found that there is a wonderful function on iTunes - Home Sharing, which allows you to stream your library to iOS devices and Apple TV. Here's the guide of how to use iTunes Home Sharing on iPhone, as well as how to use iTunes Home Sharing on iPad, iPod, etc. Follow me!
Just in case you missed the title of this article, iPhone is required to enable iTunes Home Sharing! And the following is the steps of how to enable iTunes Home Sharing on iPhone 4.
Step 1. Install the latest iTunes version. You can free download it from Apple.com.
Step 2. Click "Advanced" -> "Turn on Home Sharing" on the main interface of iTunes. Then input your Apple ID and password and click "Create Home Share", after this, Home Sharing is activated.
Step 3. Open your iPhone, and turn on an application called "Settings" on it. Under "iPhon" Settings, you will find that there is now a “Home Sharing” heading, in which you need to log in your Apple ID once again.
Step 4. Back to the iPhone app and click on the "More" tab. Next, select Library in the left-hand column and choose your shared libary from the popup menu via "Shared" option.
Note: Be sure you are connected to the same WiFi network as your PC, while you’re navigating to enable iTunes Home Sharing on iOS 5 devices.
That's all help with iTunes Home Sharing on iPhone 4. If you wanna use iTunes Home Sharing on iPod, iPad, Apple TV, etc iOS devices next time, you needn't worry what you should do any more.
More Resources about iTunes: How to Make A Podcast for iTunes, Freeware to Sync Android Phone with iTunes