How to send SMS on GSM shield - sample code not working?

Hey,

I am really new to Arduino, currently trying to program a GSM shield to send a text message. I am using the example given by the Arduino site. But I am unsure WHERE exactly to enter the phone number and text message, do you not define the char remotenum and char txtmsg beforehand?
It won't send anyway.
Can anyone tell me as well do I need an antenna attached to the GSM shield for this?7
Also the SIM doesn't have a sim code, its an Irish sim? I know Quecetel M10 on the GSM shield should work with any sim?
Using an UNO board on Windows 10.

// Include the GSM library
#include <GSM.h>

#define PINNUMBER ""

// initialize the library instance
GSM gsmAccess;
GSM_SMS sms;

void setup() {
  // initialize serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  Serial.println("SMS Messages Sender");

  // connection state
  boolean notConnected = true;

  // Start GSM shield
  // If your SIM has PIN, pass it as a parameter of begin() in quotes
  while (notConnected) {
    if (gsmAccess.begin(PINNUMBER) == GSM_READY) {
      notConnected = false;
    } else {
      Serial.println("Not connected");
      delay(1000);
    }
  }

  Serial.println("GSM initialized");
}

void loop() {

  Serial.print("Enter a mobile number: ");
  char remoteNum[20];  // telephone number to send sms
  readSerial(remoteNum);
  Serial.println(remoteNum);

  // sms text
  Serial.print("Now, enter SMS content: ");
  char txtMsg[200];
  readSerial(txtMsg);
  Serial.println("SENDING");
  Serial.println();
  Serial.println("Message:");
  Serial.println(txtMsg);

  // send the message
  sms.beginSMS(remoteNum);
  sms.print(txtMsg);
  sms.endSMS();
  Serial.println("\nCOMPLETE!\n");
}

/*
  Read input serial
 */
int readSerial(char result[]) {
  int i = 0;
  while (1) {
    while (Serial.available() > 0) {
      char inChar = Serial.read();
      if (inChar == '\n') {
        result[i] = '\0';
        Serial.flush();
        return 0;
      }
      if (inChar != '\r') {
        result[i] = inChar;
        i++;
      }
    }
  }
}

In the example code you have given it will prompt you, via Serial Monitor, which number you want to send to, and what your message is.

The line:
#define PINNUMBER "" is the one you would have to change if your SIM had a pin number, but it doesn't...

If your shield has a block attached to it with the word 'Antenova' printed on it then that is the antenna.