Switch off your phone. Now, Press POWER BUTTON VOLUME UP button for about 5 seconds. A menu should appear. Note: VOLUME UP allows to navigate the menu (move down the menu). Press VOLUME DOWN button for selecting/choosing fastboot. On your phone, it should say something
On command prompt, Type:
Now, Type the following commands:
fastboot oem unlock
fastboot format userdata
Now, your bootloader is unlocked.