[PROBLEM] ImportError: No module named RPi.GPIO

[Alfox]

Can you help me?
I 've just bought a raspberry with an electronic starter kit for raspberry called Monkmakes.
I installed Xbian on Raspberry, and now I want to try some programs to controll GPIO.
I downloaded a set of programs by their site.
One of this program is

Code:

import RPi.GPIO as GPIO
import time

# Configure the Pi to use the BCM (Broadcom) pin names, rather than the pin pos$
GPIO.setmode(GPIO.BCM)

red_pin = 18

GPIO.setup(red_pin, GPIO.OUT)


try:
    while True:
        GPIO.output(red_pin, True)  # LED on
        time.sleep(0.5)             # delay 0.5 seconds
        GPIO.output(red_pin, False) # LED off
        time.sleep(0.5)             # delay 0.5 seconds
finally:
    print("Cleaning up")
    GPIO.cleanup()

I attempt to launch this code
but there is this message:

Code:

Traceback (most recent call last):
  File "01_blink.py", line 5, in <module>
    import RPi.GPIO as GPIO
ImportError: No module named RPi.GPIO

Then I followed this guide http://www.raspberrypi-spy.co.uk/2012/05/install-rpi-gpio-python-library/
Method 2 – Manual Installation

but nothing is changed

I don't understand what I must do and I don't know the version of python, and the last version of RPi.GPIO-0.5.11