1. Hello! First of all, turn off the device by pressing the Power button.
2. Continue by pressing and holding Volume Down + Power button for a couple seconds.
3. Select the Reboot to Bootloader by using Volume buttons to choose it Power button to confirm your choice.
4. Grats, you have made it to the Bootloader Mode. It can be navigated by using the Volume buttons to scroll and Power buttons to select options.