The misconception with using an ESP to make an Arduino connected to WiFi is that the ESP is also programmable. Not really (possible, but a bit beyond the scope of this forum… see below).
It is actually just acting as a WiFi adapter, via the installed AT firmware, and your Blynk sketch, operation and I/O control is on the Arduino.
http://help.blynk.cc/hardware-and-libraries/arduino/esp8266-with-at-firmware
Now, of course of you are using a decent ESP you would probably be better off using it as a standalone Blynk device… perhaps acting as “master” to a connected Arduino “slave” that is running normal Arduino code for controlling the I/O and feeding the data back to the Blynk controlled ESP “Master”, via serial, I2C, etc. But again, the “how to” for that is not really Blynk specific.