Use the virtual pin

My project is garage door opener also it’s voice command opener .am using Amazon echo too .
I just need an LED to indicate if the door open or close or LCD to moniter in the blynk .how can I do that in Blynk am using button to open and close .
What should I add to my code to make it works
and how i can use the virtual PIN in blynk
And this is my code

// This #include statement was automatically added by the Particle IDE.
#include "blynk/blynk.h"

//#include "application.h"
#include "blynk/blynk.h"
#define GARAGE_ON D0
#define GARAGE_OFF D3
#define POWER D7

char auth[] = "xxxxxxxxxx";

void setup() {
    Particle.function("cloudFun1", fun1);


void loop() {

int fun1(String args) {
 digitalWrite(GARAGE_OFF, HIGH);
  digitalWrite(GARAGE_OFF, LOW);
 return 1;

Hello. I recommend you to start from docs it has all necessary info -

can u please give me and example I cant understand the one in the doc

so if I need to use LED in the app to light on wen D1 is on for example .

how I can write it in the code

is it like this
if (param.asInt()==0)
digitalWrite(D1, HIGH);
digitalWrite(D1, LOW);

please just how me in small cade how to

We have few examples for different cases