Facing issue while doing ADC conversion
Use the GO/!DONE bit (GO_nDONE) in the while loop, not the ADON bit. 

The library defs are in "pic16f876a.h" (or whatever processor you're using), usually found under the particular version of xc compiler in the include directory.

BTW, a 4.7K ohm resistor on a (assuming 5V) drive level will make the LED current pretty small, unless the LED is a high efficiency type it will be dim.