Mq - 7 Carbon Monoxide Sensor Help!

I have an Arduino Uno and Arduino Mega and a bunch of leds and a Mq - 7 Sensor, What i want to do is make it so when the mq - 7 sensor picks up gas (any gas) it lights an led up, The Mq - 7 uses 1 analog input. I am new it it all and have dont know much on coding. Someone please help me! =(

Here is wiring and code from Carbon Monoxide Sensor - MQ-7 - SEN-09403 - SparkFun Electronics :

http://wiring.org.co/learning/basics/airqualitymq135.html