Oprime Sync Now.
Allow several minutes for the device to begin the sync process.
Once sync begins, a revolving arrow appears in the menu bar (located in the upper-left corner).
A Syncing Media status bar appears on-screen.
Once sync completes, the time of the last sync displays.
After initially following the steps above, the iOS device syncs automatically when the following conditions are true:
The device is charging.
iTunes is open on the computer.
The device and the computer are on the same Wi-Fi network.