#define LED 2
#define BUTTON 4

int buttonState = 0; 

void setup() {
  pinMode(LED, OUTPUT);
  pinMode(BUTTON, INPUT);
}

void loop() {

  buttonState = digitalRead(BUTTON);

  // check if the pushbutton is pressed. If it is, the buttonState is HIGH:
  if (buttonState == HIGH) {
    // turn LED on:
    digitalWrite(LED, HIGH);
  } else {
    // turn LED off:
    digitalWrite(LED, LOW);
  }
}