Most Nokia Lumia Input Instructions
1 - Insert a sim card that is not from the original network.
2 - Phone will now state the following:
This sim card can only be used on specific networks. Contact your customer service center for the unlock code. (it will also display how many attempts are left).
3 - Press the Enter Pin Button and enter your unlock code we supplied you to unlock your phone.
4 - Phone is now UNLOCKED!