How to wirelessly sync your iOS5 iPhone over WiFi
Step 1 : Connect your iOS device to the computer and launch iTunes.
Step 2: Select your device from the list of devices on the left.
Step 3: Make sure the Summary tab is selected then scroll down and select Sync with this iPhone over WiFi.
Step 4: Apple changes.
Step 5: Your iPhone will automatically sync with your PC/Mac computer whenever it’s connected to a power source and both devices are on the same wireless network.