Control your LED through Blynk App using Arduino Uno.

First you have to connect LED with Arduino Uno, then HC05 or HC06 (Bluetooth Module) connect with Arduino Uno. Upload your Code & setup Blynk. Done.

Now, I am trying to explain you using a Video.

Smartphone Control Interfaces: BLYNK IoT App via Bluetooth

Controlling an Arduino from a smartphone natively requires programming incredibly complex Java/Swift applications. The BLYNK IoT Framework entirely eliminates this software friction! While Blynk is incredibly famous for Wi-Fi Internet-of-Things dashboarding, it contains a lesser-known, highly undocumented mode allowing total explicit routing over a raw offline Bluetooth HC-05 / HM-10 link! The developer utilizes the cloud-connected smartphone app to drag-and-drop massive Virtual Buttons. When pressed, the Blynk App itself natively generates the complex Serial formatting layer, blasting it via Bluetooth completely offline into the Arduino to manipulate actual physical LEDs seamlessly!

The SoftwareSerial / BLYNK Interlock Pipeline

Wiring the Bluetooth module directly to Pins 0 and 1 destroys the ability to upload new code. The process requires a pseudo-hardware port configuration.

1. The <SoftwareSerial.h> library spawns a virtual serial port natively on pins 10, 11.
2. The massive <BlynkSimpleSerialBLE.h> core library is aggressively deployed!
3. Upon boot, the Arduino completely surrenders control of the Serial listening pipeline entirely over to the Blynk firmware!

#define BLYNK_PRINT Serial    // Crucial for tracking connection bugs!
#include <SoftwareSerial.h>
#include <BlynkSimpleSerialBLE.h>

// BLYNK AUTHENTICATION TOKEN Matrix sent directly via Email!
char auth[] = "Your_123_Massive_Blynk_Auth_String";

SoftwareSerial SerialBLE(10, 11); // RX, TX to HC-05/HM-10

void setup() {
  Serial.begin(9600);     // Local Debug Engine
  SerialBLE.begin(9600);  // 2.4GHz RF Communication Engine
  
  // Violently hand over authority to the BLYNK Framework natively!
  Blynk.begin(SerialBLE, auth);
}

void loop() {
  Blynk.run(); // This executes all polling and LED actions totally autonomously!
}

BLYNK Virtual Pins (V1, V2...)

You do not explicitly write if(serial == 1) { digitalWrite(13, HIGH); } anymore!

• In the App, you drop a "Button" GUI element and link it directly to "Virtual Pin V1".
• Inside the C++ architecture, you deploy a massive BLYNK Macro: BLYNK_WRITE(V1) { ... }.
• When the App button is touched, the macro executes entirely automatically in the deep background, extracting the integer param.asInt() completely natively and firing it to the physical Digital hardware pins instantly!

RF Routing Infrastructure Components

• Arduino Uno/Nano (Serving as the fundamental bridge between BLYNK MACROS and hardware LEDs).
• HC-05 or HM-10 Bluetooth Low Energy Transceiver (Absolutely requires a 1K/2K-Ohm Voltage Divider to physically intercept the 5V TX logic signal from destroying the 3.3V Bluetooth chip!).
• Android Smartphone or iPhone executing the native generic BLYNK IoT Application.
• Physical Output Array: Relays, WS2812B LEDs, or Servos to manipulate physically utilizing the Smartphone GUI flawlessly offline without any Wi-Fi network routing necessary!