To enter a PIN unlock key on a Nokia phone, power on the device and make sure a valid SIM card is inserted, then use the phone keypad to enter the PUK code when requested. Finally, enter a new PIN code to be used in the future.
If an error message, such as Invalid PUK or Invalid SIM card, is displayed, then a new code may be required. Contact the cell phone carrier for a replacement code. Entering the PUK incorrectly too many times is likely to deactivate the SIM card, In that case, a new SIM card is required.