There are 2 ways to insert the unlock code:
1. Insert an unaccepted SIM card – One that's not from the network your phone is locked to and Turn the phone ON
2. Your Samsung will ask for the Network lock code
3. Enter your unlock code (Network/NCK) and it will say Successfully Unlocked and will now be permanently unlocked and ready for use with any GSM network in the World!
Note if Unlock Fails insert MCK/Unfreeze and after Network/NCK. If that also not work do a hard reset and repeat step 3.
Or if you don't yet have a simcard from another network you can enter the unlock code like this:
1. Turn the phone on - go to the dial screen - type #7465625*638*#
2. A screen will pop up saying "enter network lock control key"
3. Enter your the 8 digit Unlock Code we provided and press ENTER!
You will get the message Successfully Unlocked