Help with Endless mini EC-100 (boot mode)

In the same way, I just bought an Endless mini EC-100 and I need to start the computer from a USB but I cannot find a way to enter boot mode, I have already tried countless key combinations and did not succeed with any, I would like to know if it’s posible?

There is no USB boot on EC-100. If you describe what you are trying to do, we may be able to suggest alternative approaches.