Add NodeMCU ESP8266 Esp-12 to IDE

Add ESP8266 , esp-12 to IDE and use #include <ESP8266WiFi.h>

Select file >> Preferences >> paste the below URL on Additional Boards Manager URLs

URL : http://arduino.esp8266.com/stable/package_esp8266com_index.json

Select Tools >> Board: >> Boards Manager

Type ESP-12 on search the click install

Download the Library from this link : https://www.mediafire.com/file/srd112xd57mrm7k/ESP8266WiFi.zip/file

Extract the file on IDE Location on your computer

as an example C:\Program Files (x86)\Arduino\libraries

Select your board from tools update its data port, speed, etc