How to Update iTunes on an Unlocked iPhone
- 1). Open iTunes on your computer by clicking "Start" > "All Programs" > "iTunes" > "iTunes."
- 2). Plug your unlocked iPhone to your computer using the iPhone's USB charger cord. Even though your iPhone is unlocked, it will still be recognized by iTunes and appear on your iTunes device list.
- 3). Sync the iPhone with your iTunes library so that iTunes backs up and syncs your iPhone. Usually this happens automatically when you plug in the phone but if not, you can just click “Sync.”
- 4). Click “Download Update.” If there is a new update for your iPhone, iTunes will tell you so and ask you to download and install the update. Once the update downloads, iTunes will automatically install it onto your iPhone and re-sync the phone.
- 5). Wait for iTunes to finish updating your phone and then unplug it once the sync has completed. Note that once your iPhone is done updating, it will be locked and no longer jailbroken.
Source...