Unlocking the bootloader is a part of the rooting process. Users need to unlock the bootloader, then install the TWRP using fastboot and then root the device using Magisk or SuperSu.

fastboot oem unlock Now navigate to “ Unlock the bootloader ” option by using the volume button and select it with the power button. The bootloader will be unlocked after the device reboots.

All you have to do is enable ADB debugging, reboot into the bootloader, and run the same “fastboot oem unlock” command that you’d use to unlock the bootloader on a Nexus device.