For Seniors: Update Software on Your iPhone 4S
Apple occasionally updates the iPhone 4S system software to fix problems or offer enhanced features. You should occasionally check for an updated version (say, every month).
Start by connecting your iPhone to your computer.
On your computer, open the iTunes software you installed.
Click on your iPhone in the iTunes source list on the left.
Click the Summary tab.
Click the Check for Update button. iTunes displays a message telling you whether a new update is available.
Click the Update button to install the newest version.
Note that with iOS 5 and iCloud you can also tap Settings, General, and then tap Software Update. Your phone will go out and look for and update and install it for you.
If you’re having problems with your iPhone, you can use the Update feature to try to restore the current version of the software. Follow the preceding set of steps, and then click the Restore button instead of the Update button in Step 6.
If you’ve chosen to back up and restore iPhone via iCloud when you first set up the device, restoring and updating your device happens automatically.