int ledPin1 = D2; // initialize pin D2 where LED 1 is connected to
int ledPin2 = D3; // initialize pin D3 where LED 2 is connected to

void setup() {
  // We want to tell the Argon that we'll use
  // D2 and D3 as output pins.
  pinMode(ledPin1, OUTPUT);
  pinMode(ledPin2, OUTPUT);

}

void loop() {

  digitalWrite(ledPin1, HIGH);   // Turn ON the LED 1 pins
  digitalWrite(ledPin2, LOW);   // Turn OFF the LED 2 pins
  delay(1000);               // Wait for 3000mS = 3 seconds

  digitalWrite(ledPin1, LOW);   // Turn ON the LED 1 pins
  digitalWrite(ledPin2, HIGH);   // Turn OFF the LED 2 pins
  delay(1000);               // Wait for 3000mS = 3 seconds

}