iOS Firmware/IPSW File Downloads for all iPhone, iPod Touch, iPad and Apple TV models.
Use the following steps to check which version of firmware is installed on your device. Tap Settings > Tap General > Tap About > Your current running iOS firmware will be listed next to Version.
Updating or Restoring Your Device with New iOS Firmware (IPSW) Files
Restoring your device will delete all data and content, including videos, songs, photos, contacts, and other information, and will restore all settings to their factory condition. Updating your device doesn’t affect your content, settings or other information. In either case, I recommended that you back-up your content in iTunes before beginning the process.
After downloading the desired firmware, connect the device to your computer and select it in iTunes. Mac users hold down the Option key, while Windows users should hold down the Shift key. Then click on the Update or Restore button, select the IPSW file you recently downloaded and click Choose. Your device should now begin to update. Take note that certain browsers may change the ipsw-file into a zip-file. If this should occur, just rename it to end in .ipsw and iTunes will recognize it.