Controlling multiple servos and servo driver through Blynk
I'm guessing the servo.attach() command is for connecting a servo to the ESP8266 directly.

If that's true then you will need a totally different driver (aka include file), to control the servos.

If there's one available, then great you're done. But if not..

First look at the tutorial on Adafruit. That will tell you how to talk to the driver over I2C. You might have to just look at the source code of their arduino library. It shouldn't be too complicated.

Then you need to look at some tutorials for the ESP8266 or Blynk, you can use these to figure out how to send the I2c data you determined in the last step.