ESP8266 Wi-Fi connection setup

Thanks for your answer!So, I'll go with SW v2.0. I'll follow the steps from instruction how to flash the GK-WiFi board using ftdi adapter, but when open GK-WiFi_v2_0 folder, there are few other files. Should I open all of the .ino files in the Arduino IDE, or just GK-WiFi_v2_0.ino file and fill the new credentials? Do I need some libraries, or only those from the build instructions (Step 2)?

Okay, I installed the ESP8266 board from the Board Manager. Loaded the file, but got an error, and the compilation terminated. Do you have any suggestions on what I can do, please? Can I load it this way?

  Sooo.... I manually included libraries in C:\Users\emili\Documents\Arduino\libraries, and now the red row is gone, and Fatal error is no longer written. Of course, other warnings came. I'm still trying to compile with no board connected via FTDI, that's why the last row is there, I believe. What do you think those warnings mean? Should I change something or try uploading with new credentials filled?

Well, after reading User Notes left in the sketch, executing the recommendations written there, Compiling was done with no Errors.

Now, I have to try it with the board plugged into the PC and to load the file. Will left a comment after that.

Mission accomplished!

Finally, I managed to set new SSID and password. In addition to feeding Radmon, I started feeding ThingSpeak as well (I had to register a new channel there).
Initially I flashed the ESP8266 with sw_v2_0, but I didn't like the OLED screen layout, so I flashed sw_v1_7 back (that was the stock version of the GK-WiFi kit software when I bought it). Seems that there is no problem for board v1.2 to works flawless with sw_v2_0