Here's an example of reading an analog voltage with a 12F683. I'll let you figure out the LED part...;}
Code:
@ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF

    DEFINE OSC 8            ' Internal 8MHz 
    DEFINE DEBUG_REG GPIO   ' Define DEBUG port
    DEFINE DEBUG_BIT 1      ' Set GPIO.1 as DEBUG serial output pin
    DEFINE DEBUG_BAUD 9600  ' DEBUG baud rate = 9600 bps
    DEFINE DEBUG_MODE 1     ' 1 = inverted, 0 = true
    
    DEFINE  ADC_BITS 10     ' 10-bit resolution
    DEFINE  ADC_CLOCK 5     ' Set clock source to Frc/16
    DEFINE  ADC_SAMPLEUS 50 ' Sample time in uS before A/D conversion is started
    Quanta  CON 1251        ' For 10-bit A/D +Vref = 5V : 5V/1023*256=1.251=Quanta

' PIN# NAME     USE & CONNECTION
'  1   Vdd      +5VDC power supply
'  2   GPIO.5   N/C (N/C = NO CONNECTION)
'  3   GPIO.4   N/C
'  4   GPIO.3   N/C
'  5   GPIO.2   N/C
'  6   GPIO.1   Serial output pin to PC serial port RX pin
'  7   GPIO.0   A/D input pin
'  8   Vss      Power supply ground (also connect to DB-9 pin #5)
'-------------------------------------------------------------------------

    CMCON0 = 7          ' Disable comparator
    ANSEL = %00000001   ' Set GPIO.0 to A/D
    ADCON0.7 = 1        ' Right justify for 10-bit
    TRISIO = %00000001  ' GP.1 = serial out, GPIO.0 = A/D in, rest outputs
    OSCCON = %01110000  ' Internal 8MHz osc
    ADval  VAR WORD	' A/D conversion result

MAIN:
    ADCIN 0, ADval      ' Read A/D
    ADval = ADval */ Quanta
    DEBUG DEC ADval DIG 3,".",DEC3 ADval,"~"
    PAUSE 200
    GOTO MAIN

    END