1 step: ROOT
At the beginning you need to root with that way:
http://forum.gsmhosting.com/vbb/f777...-mini-1640319/
2 step: DEBUGGING
Always be sure you installed all drivers correct and enable in Settings - Applications - Unknown Source and in Development - USB Debugging.
3 step: SAMSUNG TOOL Z3X
Before you push UNLOCK, you have connected the mobile in USB mode. During the process you need to change to UART CABLE
Example:
Reading phone info...
Model: GT-I8190
Android version: 4.1.1
Product code: GT-I8190MBACNX
Phone version: I8190XXALJL
PDA version: I8190XXALJL
CSC version: I8190OXAALJL
IMEI: Unknown
Checking Super user right... true
Reading data from phone... OK
Now connect phone to UART cable
Checking phone at COM7 OK
Bypass MSL... OK
Unlocking... OK
Unlock done
Codes set to 00000000
Done with Samsung Tool v.14.0
If phone asks for code enter 00000000
UNLOCK OK!