Now that you have the main electronic installed, you can install it on the motor - that will rotate all the platform (the matrix).
What you need is a simple DC motor (preferable with a removable shaft adapter), a piece of wood and two small screws.
I marked on the wood the required width I needed, the location of the holes for the bolts and for the shaft from the motor.
Then I drilled and sawed upon the marks.
I used the holes in the matrix to attach the wood to the matrix - using the bolts.
Note that the bolts must be long enough to grab the matrix - without passing to the other side and damage the Arduino.
I have inserted the shaft adapter into the drilled hole - using some force. The insertion planned to be "press fit" since the forces the shaft feels are not negligible.