People have pointed you to good resources, however you do have to do some work yourself. Here are some pointers to get you going
1) If you use the code from here - http://rcarduino.blogspot.com/2012/01/how-to-read-rc-receiver-with.html
It should print the RC Input value to the serial monitor, have you done this ?
2) If yes to 1) after then after the line Serial.println(nThrottleIn); you can add some code to turn one LED on if nThrottle in > 1500 and the other LED on if nThrottle in < 1500.
Over to you,