Place the leds near the edge of the matrix, so the circle it draws will be as wide as possible.
Note the polarity of the leds to be oriented in the same direction.
(You can use leds in different colors as I did with the WOOOSH case).
Place the Arduino near the center of the matrix and mount it to the matrix.
I used simple wires for that.
Since the bottom part of the Arduino has some conductors - I used a piece of plastic sheet as an isolator from the matrix.
Connect one side of the leds to the IO of the arduino (ports 1-7, leaving port 0 for the trigger).
Use suitable resistors and connect the other leg of the leds to the ground.
I used the bottom rail of the matrix as a common ground.
I used 420 Ohm resistors.