Send a GO command via Mac Terminal to my Ardunio Pro/Bluetooth Mate Silver

I have the BT module paired and running. I have a working serial port /dev/tty.RN42-B86B-SPP

What do I type into Mac Terminal program to get the serialEvent() to run?

/*
  Serial Event example
 
 When new serial data arrives, this sketch adds it to a String.
 When a newline is received, the loop prints the string and 
 clears it.
 
 A good test for this is to try it with a GPS receiver 
 that sends out NMEA 0183 sentences. 
 
 Created 9 May 2011
 by Tom Igoe
 
 This example code is in the public domain.
 
 http://www.arduino.cc/en/Tutorial/SerialEvent
 
 */

String inputString = "";         // a string to hold incoming data
boolean stringComplete = false;  // whether the string is complete
#include <Servo.h> 
Servo balldropservo;  // create servo object to control a servo 
                // a maximum of eight servo objects can be created 
 
int pos = 0;    // variable to store the servo position 

void setup() {
  // initialize serial:
  Serial.begin(9600);
  // reserve 200 bytes for the inputString:
  inputString.reserve(200);
  balldropservo.attach(9);  // attaches the servo on pin 9 to the servo object 
    pinMode(13, OUTPUT); 
}

void loop() {
  // print the string when a newline arrives:
  if (stringComplete) {
    Serial.println(inputString); 
    // clear the string:
    inputString = "";
    stringComplete = false;
  }
}

/*
  SerialEvent occurs whenever a new data comes in the
 hardware serial RX.  This routine is run between each
 time loop() runs, so using delay inside loop can delay
 response.  Multiple bytes of data may be available.
 */
void serialEvent() {
  while (Serial.available()) {
  digitalWrite(13, HIGH);   // set the LED on
  delay(1000);              // wait for a second
  digitalWrite(13, LOW);    // set the LED off
  delay(1000); 
  }
}

The serialEvent() method is called once per iteration of loop(), if there is serial data to be processed. In that event, you are supposed to actually read the data.

  // reserve 200 bytes for the inputString:
  inputString.reserve(200);

If you don't even know what to type, why are you reserving 200 bytes for that data?

You never actually put anything in inputString, and you never set stringComplete to true. What are they for, if you are not going to set the values?

Thanks for the reply Paul. I just copied this code from an example because it seemed to be close to what I needed. My goal is to trigger a set of commands (in this case making the light blink) from my Mac.

I assume I can use the built in terminal program. Just not sure what I type in to terminal to trigger the ardunio sketch.

Just not sure what I type in to terminal to trigger the ardunio sketch.

Anything you type will be sent to the Arduino. You also need to program the Arduino to read, parse, and use the serial data. It does not do that automatically.