int ledPin1 = D2;
int ledPin2 = D5;

void setup() {
      // We want to tell the Argon that we'll use D2 and D5 as output pins.
    pinMode( ledPin1, OUTPUT);
    pinMode( ledPin2, OUTPUT);
}

void loop() {
    digitalWrite( ledPin1, HIGH ); //turn LED1 on
    digitalWrite( ledPin2, LOW ); //turn LED2 off
    delay(2000); //wait for 2 second2
    digitalWrite( ledPin1, LOW ); //turn LED1 off
    digitalWrite( ledPin2, HIGH ); //turn LED2 on
    delay(2000); //wait for 2 second2
    // rinse + repeat
}