This post is about how to set fixed IP for ESP8266 and how to check the result.
Arduino Sketch
The sketch used is the "AutoConnectWithStaticIP" sketch that comes with the WiFiManager library. Be sure to select the right block (block1 or block2) according to the version of the ESP8266 core installed on your computer.
For my case, I have version 2.4.1 installed, so I used block1.