a little help with arduino mega 2560 and cellular shield

i have arduino mega 2560,cellular shield and module sm5100b.

i have 2 cables from cellular shield (d2 and d3) connect to arduino Rx and Tx.

another cable from cellular shield 5V to arduino 5V (power)

another cable from cellular shield Ground to arduino Ground

It gets power from my laptop

my project is send SMS using arduino

I would like to know, how many LED has to be ON at cellular shield and what color.The arduino has always 1 led green ON and when I send command the led of tx is put ON after is off

because I did all this and nothing happen

#include <string.h> //Used for string manipulations

char incoming_char=0; //Will hold the incoming character from the Serial Port.

void setup()

{

//Initialize serial ports for communication.

Serial.begin(9600); // for terminal communication

Serial1.begin(9600); // for GSM module communication

Serial.println(“Starting SM5100B Communication…”);

}

void loop() {

//If a character comes in from the cellular module…

if(Serial1.available() >0)

{

incoming_char=Serial1.read(); //Get the character from the cellular serial port.

Serial.print(incoming_char); //Print the incoming character to the terminal.

}

else

{

Serial.println(“Es AAA”);

}

//If a character is coming from the terminal to the Arduino…

if(Serial.available() >0)

{

incoming_char=Serial.read(); //Get the character coming from the terminal

Serial1.print(incoming_char); //Send the character to the cellular module.

}

else

{

Serial.println(“Es BBB”);

}

}

the answer on the screen is “Es AAA” and “Es BBB”

I type the command AT and nothing happen

could somebody tell me what is wrong right here or send me link to see how all has to be connect together

thank in advance