Firstly, lets check that you have connected your LDR up correctly, it should be something like this...
To read the value of PIN RA0/AN0, you need to do some initialisation to make sure the port is setup correctly. The datasheet explains how all this works, but these values should work:
TRISAbits.TRISA0 = 1; // Set RA0/AN0 to input
ADCON0 = 0b00000000; // Set channel select to AN0
ADCON1 = 0b00001110; // Configure RA0/AN0 as analogue
ADCON2 = 0b10101010; // Right justified result
// TAD 12 and FOSC 32 - may need to adjust this
// depending on your clock frequency (see datasheet)
ADCON0.ADON = 1; // Enable ADC
Now the port should be set up, you can now read the LDR value:
ADCON0bits.GO = 1; // Set the GO bit of the ADCON0 register to start
// the conversion.
while (ADCON0bits.GO); // Wait until the conversion is complete.
You can now read the result of the LDR as a 10-bit value in
ADRESH:ADRESL. If you only need 8-bit resolution, then set
ADCON2.ADFM = 0 for left justification of the result, then you only need to read the
ADRESH to get your result.