This guide demonstrates the FOTA (Firmware-Over-The-Air) function for ESP8266-based devices. In particular, the guide outlines the process of upgrading ESP8266 firmware from Espressif Cloud over Wi-Fi by using our Android app. This process requires no technical skills and does not involve a PC or UART based tools. Therefore this process can be carried out by any user, including end users of ESP8266 based products. The FOTA test has been demonstrated and run on the ESP-Launcher, an ESP8266 evaluation board designed by Espressif.