Perhaps this will help you:
Before setting up syncing you should download and install the latest version of iTunes. Wi-Fi syncing requires iTunes 10.5 or later and iOS 5 or later. You can change your sync options at any time. Each time you sync, content is synced between your iOS device and computer to reflect new, updated, or deleted content.
USB syncing
Open iTunes.
Connect the iOS device to your computer using the included USB cable and select it in iTunes under Devices on the left-hand side.
Click Apply, in the lower-right corner of the screen, to sync.
Wi-Fi syncing
Open iTunes
To set up Wi-Fi syncing, connect your iOS device to your computer with the included USB cable. Select your device under Devices on the left-hand side.
In the Summary tab, select "Sync with this [device] over Wi-Fi".
Whenever the computer and the iOS device are on the same network, the iOS device will appear in iTunes, and you can sync it. The iOS device will sync automatically when all of the following are true:
The iOS device is plugged in to power
iTunes is open on the computer
The iOS device and the computer are on the same Wi-Fi network
While the iOS device appears in the left-hand column of iTunes, you can select the content tabs and configure sync options.
Click Apply or Sync to sync the iOS device.