The USBC-PDMON can be powered solely by a USB Type-C connection to the host device, however that USB Type-C connection must be capable of providing 15W of power in order for this to work.
Small devices such as phones or tablets may not be able to provide 15W, and if that is the case the monitor must be powered by an external power source that can provide up to 15W of power (for example a charger that supports USB Power Delivery at a minimum of 15W).