CPP: Installation - lvidarte/esp8266 GitHub Wiki

The ESP8266 Arduino core could be installed in the Arduino IDE as following, but there is more interesting IDE you can use to develop your firmware for the esp8266, and Arduino too!:

PlatformIO

PlatformIO is an open source ecosystem for IoT development with cross platform build system, library manager and full support for Espressif (ESP8266) development. It works on the popular host OS: macOS, Windows, Linux 32/64, Linux ARM (like Raspberry Pi, BeagleBone, CubieBoard).