You can set up iTunes to automatically update the music and video on your iPod, iPhone, or iPad when you connect your device to your computer.
If you want more precise control over the content you add, or if you want to use your iPod with more than one computer, you can choose to manage your music and video manually. Your iPhone or iPad can be managed with only one computer, even if you manage your content manually.
The first time you connect your iPod, iPhone, or iPad, you choose between automatically syncing or manually managing your content, but you can change the setting any time your device is connected to your computer.
To sync music and video to your iPod, iPhone, or iPad automatically:
1 Connect your iPod, iPhone, or iPad to your computer and select your device in iTunes (below Devices).
2 Click the Music tab and choose your options for automatically syncing songs and playlists:
To choose your options for automatically syncing video, click the Movies or TV Shows tab.
To start syncing, click Apply.
iTunes uses these settings until you change them. If you sync multiple devices with different settings, iTunes saves the different settings for each device. You can change your sync settings any time your device is connected to your computer.
If you choose automatic syncing, you can't add songs by dragging. To manage your music and video manually:
Connect your iPod, iPhone, or iPad to your computer and select your device in iTunes (below Devices).
Click the Summary tab and select "Manually manage music and videos" (below Options).
Select Music, Movies, or TV Shows (below Library).
Drag songs, videos, and playlists to your iPod, iPhone, or iPad (below Devices).
Before you disconnect your iPod, iPhone, or iPad, click the Eject button:
If you manage your music manually, you can also fill your device with a single click by using Autofill.