Installing ESP8266 Board in Arduino IDE

Before starting you need to install latest Arduino  IDE software. If you don't installed Download first

Arduino IDE - https://www.arduino.cc/en/software

Install ESP8266 in Arduino IDE

1. In Arduino first go to the file > Preferences

2. Enter 

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

in the "Additional Boards Manager URLs"  and click "OK".

3. Then,  Go to tools > Boards > Board Manager .

4. Search for ESP8266 and install ESP8266 Board by ESP Community.

5. That's All