1. Hello. Please press the Power button to turn your phone off.

2. Now press & hold the Volume Down and Power button for a few seconds.

3. Let go of these buttons when a new menu shows on screen.
4.Using Volume buttons to select and Power button to confirm your choice, choose the Reboot to Bootloader.

5. Now choose, in the same way as above, a Reboot to Recovery Mode option.

6. When in Recovery mode, navigate using Volume buttons and select options with Power button.