Problems for using RFID-RC522 Reader/Writer

Using Arduino Project Guidance
1

I am a newbie for using Arduino. I bought a RFID reader (RFID-RC522) and connected it with Mega 2560. I have installed the library and after connecting it, i can't see anything in the serial monitor after putting RFID tags on the reader.It is supposed to read the serial number of each tags and show it on the serial monitor. just don't know why and hope someone can provide me some solutions. Here is my pin connection and my code:

MOSI: Pin 51
MISO: Pin 50
SCK : Pin 52
SS : Pin 53
RST : Pin 5

/*
 * MFRC522 - Library to use ARDUINO RFID MODULE KIT 13.56 MHZ WITH TAGS SPI W AND R BY COOQROBOT.
 * The library file MFRC522.h has a wealth of useful info. Please read it.
 * The functions are documented in MFRC522.cpp.
 *
 * Based on code Dr.Leong   ( WWW.B2CQSHOP.COM )
 * Created by Miguel Balboa (circuitito.com), Jan, 2012.
 * Rewritten by Søren Thing Andersen (access.thing.dk), fall of 2013 (Translation to English, refactored, comments, anti collision, cascade levels.)
 * Released into the public domain.
 *
 * Sample program showing how to read data from a PICC using a MFRC522 reader on the Arduino SPI interface.
 *----------------------------------------------------------------------------- empty_skull 
 * Aggiunti pin per arduino Mega
 * add pin configuration for arduino mega
 * http://mac86project.altervista.org/
 ----------------------------------------------------------------------------- Nicola Coppola
 * Pin layout should be as follows:
 * Signal     Pin              Pin               Pin
 *            Arduino Uno      Arduino Mega      MFRC522 board
 * ------------------------------------------------------------
 * Reset      9                5                 RST
 * SPI SS     10               53                SDA
 * SPI MOSI   11               52                MOSI
 * SPI MISO   12               51                MISO
 * SPI SCK    13               50                SCK
 *
 * The reader can be found on eBay for around 5 dollars. Search for "mf-rc522" on ebay.com. 
 */

#include <SPI.h>
#include <MFRC522.h>

#define SS_PIN 53
#define RST_PIN 9
MFRC522 mfrc522(SS_PIN, RST_PIN);	// Create MFRC522 instance.

void setup() {
	Serial.begin(9600);	// Initialize serial communications with the PC
	SPI.begin();			// Init SPI bus
	mfrc522.PCD_Init();	// Init MFRC522 card
	Serial.println("Scan PICC to see UID and type...");
}

void loop() {
	// Look for new cards
	if ( ! mfrc522.PICC_IsNewCardPresent()) {
		return;
	}

	// Select one of the cards
	if ( ! mfrc522.PICC_ReadCardSerial()) {
		return;
	}

	// Dump debug info about the card. PICC_HaltA() is automatically called.
	mfrc522.PICC_DumpToSerial(&(mfrc522.uid));
}

Any help is appreciated

2

Hello. I am new to the world ARDUINO. I'm using the first RC-522 module. I found this app and I yours based on it to build my program. The problem is that I have no MFRC522.h library. If you're so kind, you could pass the library folder to install on my computer.

Thank you very much.

PS: sorry for my very bad english, I'm from Argentina and I am using Google Translate to communicate with you.

3 
// Look for new cards
	if ( ! mfrc522.PICC_IsNewCardPresent()) {
		return;
	}

What is it returning here? I dont see anything!