1. Connect your iPhone to the computer with via a USB cable that your iPhone has trusted.
2. Launch iTunes. If you’ve synced your iPhone with iTunes, then no “enter password” is required.
3. iTunes will automatically sync your iPhone and create a backup file. If it doesn’t, you should sync your iTunes and create a backup file manually by in the Summary window.
4. In the Summary window, you can see the option “Restore iPhone”. Click it and follow prompts to choose the latest iTunes backup to restore your iPhone.
Reset iPhone Password via iTunes
After the restoration process is complete, your passcode will be erased and all your data will be restored from your backup. You will now be able to access your iPhone without any passcode. And you can set your new password on iPhone.
Feel free to know more methods about resetting password on iPhone. http://www.leawo.org/tutorial/how-to-reset-password-on-iphone.html