Setup Blynk on your Smartphone

The first thing you will need to do is to install the Blynk app from either the Google Play Store (Android users) or the Apple store (iPhone users). Once you have installed it, sign up using an e-mail address that you have access to. This e-mail will be were you are sent the authentication for your projects.

(signup for Blynk)

Once you have signed up, create a New Project by tapping on the "+" icon. Name your Project "IoT light Switch"; Choose NodeMCU under device and choose "WiFi" under connection type then tap the create button at the bottom.

Tap on the "+" icon and add a button. Click on the button to get options to configure and set it up.

Adding a button widget

Button widget

Name the button "Light Bulb" and assign the output pin to digital pin 0 i.e. DO and set the logic to be 0-1.

Assigning the digital pin to the botton