We will use Blynk app to control our on board LED of Arduino UNO. In Blynk you can connect it to cloud and by installing Blynk libraries and providing author token you can have access to your board.
Sign in to Blynk app and create a new project.
Give a name to your project. Choose device as Arduino UNO. Select Connection type as USB.
Check your E-mail for Author Token.
Select "ADD DEVICE" and add Button. Click on button you added. There opens Button Manager. In output select Digital 13th pin.
In Code copy and paste your Author Token.
Open Command Prompt. Write
cd "Your Blynk Scripts address"
then press enter.
Now write blynk-ser.bat -c COM3 or any com your device is connected. Press enter. Now you can control your device with Blynk.