Update ESP8266_Spectrum_Display_01.ino

ESP8266_Spectrum_Display_01.ino

@@ -15,6 +15,7 @@
 
 #include <Wire.h>
 #include "arduinoFFT.h" // Standard Arduino FFT library
+// https://github.com/kosme/arduinoFFT, in IDE, Sketch, Include Library, Manage Library, then search for FFT
 arduinoFFT FFT = arduinoFFT();
 /////////////////////////////////////////////////////////////////////////
 // Comment out the display your nNOT using e.g. if you have a 1.3" display comment out the SSD1306 library and object