That link didn't work.
You need 3 things:
1) The "receiver" portion, which is the structure that bolts to the frame or unibody of the vehicle.
2) The "hitch/ball mount" portion, which is the part with the ball on it that slides/locks into the receiver.
3) Wiring harness to connect the vehicle signal/brake/tail lights to the trailer lights.
If you're just planning to move a tiny trailer at low speeds and not on public roads, you could maybe make a simple ball mount to the car with some angle iron or something.
I seem to remember Daox's Aveo came with a home made thing like that... lemme see if I can find it.