Preparations you will need to make on your Samsung before we can do the unlock :
Go to Settings > Developer Options and enable USB Debugging ON and OEM Unlocking (if available)
If "Developer Options" is not showing in Settings,go to Settings > About Phone > Build number > Tap it 7 times untill you will see the message "You are now a developer!".After that go back to Developer Options and enable USB Debugging ON .
If you have android version 2.36 or lower to enable usb debugging settings go to:
Go to Menu - Settings->Applications> Development