If you have performed steps 2 and 3 correctly, your PC will automatically discover your board as an attached USB-device.
Now all you need to do is to click the Start button and wait for burning to complete.
To interrupt burning, click the Stop button, then close the USB Upgrade Tool. Note that the eMMC may already have been completely erased if you went past the 15% mark.
An External Power Supply may be required in cases where your PC cannot provide enough electrical power for the burning process.