Can you please describe your problem with more details. Otherwise, if the problem is that iTunes will not let you update your iDevice, follow the steps below.
1. Make sure your iDevice is charged before continuing to the next step.
2. Connect your iDevice to your computer.
3. Open iTunes. (If it doesn't open automatically.)
4. Your iDevice should appear in the iTunes windows.
5. Click on your device.
6. Click "Restore" on the device page in iTunes.
7. Download the iOS firmware file.
8. After the download finishes, a dialog bog will come up. Click "Restore and Update".
9. Wait for the restore to complete.