connect phone to pc (while in normal system)
then open cmd window inside adb folder
type: adb devices (should give you a number)
then: adb reboot bootloader (phone shuts down and loads into white screen - as in your screenshot)
then: fastboot devices (should give you numbers again - this makes sure your phone is seen by the pc)
then: fastboot oem unlock xxxxxxxxx (16digit)..
(maybe you try the uni code - works not for all huawei devices): UUUUUUUUUUUUUUUU (16x letter "U" capital)..