1. Hi. Start by turning off the phone. To do that, press and hold the Power button.
2. When the phone is turned off, press and hold Volume Down & Power button.
3. Let go of these buttons when a Boot Mode menu shows on screen.
4. Using Volume Up to scroll and Down to confirm your choice, select the Fastboot option.
5. Superb, you are now in Fastboot mode. Navigate this mode using Volume Keys; select options with Power button.