The basic blink sketch is the easiest project to build but don't under estimate it. This sketch can be extremally useful to determine if you have a problem with your board. On the image above is highlighted the BUILTIN_LED for this board, it is connected to GPIO13 and you can use either the GPIO number or the BUILTIN_LED defined name to access it.

Code:
 /***
* Basic control of output pin
* flashes either the on-board LED or a
*second LED connected to GPIO D2
***/

void setup()
{
  pinMode(BUILT_IN, OUTPUT);
  pinMode(2, OUTPUT);
}

void loop()
{
  digitalWrite(BUILTIN_LED, HIGH);
  digitalWrite(13, LOW);
  delay(1000);
  digitalWrite(BUILTIN_LED, LOW);
  digitalWrite(13, HIGH);
  delay(1000);
}