Ive been searching around some more now and I think the way to do this is using;
Serial Communication
Used for communication between the Arduino board and a computer or other devices. This communication happens via the Arduino board's serial or USB connection and on digital pins 0 (RX) and 1 (TX). Thus, if you use these functions, you cannot also use pins 0 and 1 for digital i/o.
Serial.begin(speed)
Serial.available()
Serial.read()
Serial.print(data)
Serial.println(data)
this stuff to read signals sent from the serial library that is available for Processing. Does that make sense?