Start iTunes
Start the program iTunes on your computer.
Connect phone and computer
Connect the data cable to the socket at the bottom of your phone and to your computer's USB port.
Update the phone software
Depending on your settings in iTunes, the program may suggest to update your phone automatically.
To start the update manually:
Select your phone on the list of connected devices.
Select your phone on the list of connected devices.
Select Check for Update.
Follow the instructions on the screen to update the phone software.
Follow the instructions on the screen to update the phone software.