First make sure to enable USB debugging in Android ([https://www.kingoapp.com/root-tutorials/how-to-enable-usb-debugging-mode-on-android-5-lollipop.htm])
Then with device powered off, hold down Volume-Down and Power buttons simultaneously for a few seconds, until Fastboot Mode screen appears.
Then with device powered off, hold down {{button|VolumeDown}} and {{button|Power}} buttons simultaneously for a few seconds, until Fastboot Mode screen appears.