Download the library BETA_GSM_GPRS_GPS_IDE100_v307_1.zip
Extract the file and copy paste the extracted file to the path you install the arduino software, for example programfile/arduino/libraries
Select the right jumper (the red circle) to use with arduino uno. The jumper indicate that you are using TX RX at pin 2 and pin 3.
Open the Arduino software and compile this code into arduino uno.
To use this coding, wait until the SIM900 shield initialize by waiting the LED at pin 13 turn ON.
When it is turn on, you can sent sms "Led off" to the simcard number to turn it off.
#Arduino UNO + SIM900 shield + LCD sheild
#Setting LCD Shield
You need to setting up the hardware because the pin of LCD shield and sim900 shield clash at pin 8 and pin 9.
Then, you can compile this code into arduino uno.
After you had compile it, disconnect the usb cable from the arduino uno and you will be using external power to the arduino uno as shwon below.
Connect the external 12V or 9V power, and now you can play with it after waiting until the SIM900 sheild initialize.
Button down(Read SMS)
Button left(PickUp Call)
Button Right(HangUp Call)