You should always use the latest version of iPhone software on your device. You do this through iTunes and have two options: to update the device or to restore it.
- The software is updated but your settings and any songs you have on the device are not affected.
- All data is erased from the device, including songs, videos, contacts, photos, and calendar information; all original settings are restored.
To update or restore your device, follow these step:
- Make sure your PC or Mac has an Internet connection and you have the latest version of iTunes installed on it (apple.com/itunes/download).
- Connect the iPhone/iPod touch to a PC or Mac.
- In iTunes, select iPhone or iPod in the Source list and click on the Summary tab.
- Click on “Check for Update” and iTunes will tell you if there’s a newer version of the iPhone or iPod software available.
- Click on “Update” to install the latest version of the software. Click on “Restore” to restore the iPhone or iPod to its original settings and erase all data.
- Follow the onscreen instructions to complete the restore process.