To start building your first IoT projects:
Use supported hardware (ESP32, Arduino, Raspberry Pi, etc). List of supported devices is here.
Installed Blynk.Edgent (a hardware library)
It's expected that you are familiar with basics of electric circuitry and know how to at least blink an LED using Arduino boards, know how to install libraries, etc.
If you have all of the above ready, you can jump directly to this article
or read more about the main concepts and elements of Blynk IoT platform: