Getting Started To Use NodeMCU (ESP8266) With Arduino IDE: http://blog.vaibhavpandey.com/2018/09/getting-started-to-use-esp8266-nodemcu.html

LED_Blink.ino

int BLINK_SPEED_MS = 250;
int PIN_N = 15;

void setup() {
  // put your setup code here, to run once:
  pinMode(PIN_N, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(1000);                // pause for a second
  for (int i = 0; i < 5; i++) {
    blink(BLINK_SPEED_MS);    // blink 5 times
  }
}

void blink(int wait) {
  digitalWrite(PIN_N, HIGH);  // supply voltage to pin
  delay(wait);                // wait
  digitalWrite(PIN_N, LOW);   // power down
  delay(wait);                // wait
}