AYAB hardware comes in two versions, known as the shield and interface versions. Electronically they are the same, except that they use different flavors of the Arduino chip, so they need different drivers. The Arduino is soldered onto the interface, in the shield version it's a separate board that sits underneath.
The Arduino itself is powered from the USB cable. For the power connection to the machine's patterning mechanism, follow the installation instructions that came with your hardware.
See also: https://vimeo.com/99870358 Click the CC button to see subtitles in English. And for the interface; https://wiki.evilmadscientist.com/AYAB_Hardware_Installation
Very Important: In the shield version, you have to isolate the USB of the Arduino from the Power Connector to prevent short circuits!!