This is a basic Arduino code to get two wheels to rotate. This project uses continuous rotation servo motors. Although I am using a motor driver board with my Arduino, in actuality a driver board is NOT needed. The pictured BRAIN PAD is not used in this example, so ignore it.
See code below. The important thing to know is that the Write code controls the speed and direction of motor from 0 to 180. The midpoint is 90, which indicates stopped motor.