1. Make sure that your PC is installed drivers fastboot, and adb.
2. Turn on the "Debug mode" settings for the developers. (To activate the settings for the developers, press 7 times on the "build number" in the "About phone")
3. Turn on the "factory unlocked" settings for developers.
4. Connect the device to your computer via USB.
5. Open a command prompt and reboot the device in fastboot mode by using the command.
fastboot oem unlock-go
6. When the device is loaded into the fastboot mode, check the connection with the command
If you do not see in the list of the number of your device, but instead see "<waiting for device>", it means you have not installed the driver fastboot
If you see "no permissions fastboot ", try to start a command prompt as an administrator
7. Enter the command to unlock the bootloader