Add ESP8266 and add library files in the arduino additional development board management website

 

As shown in the figure above, add the following address in "Additional Development Board Management URL"

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

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

Or the link recommended by the official github

http://espduino.doit.am/package_esp8266com_index.json

 

 

As shown above, open the "Development Board Manager"

 

 

 

As shown above, pull down to find esp8266, install