@doggy, apart from what Eric and Burt have said, the Analog input should be on an Analog input which would require you to configure the AD Module. Than as Eric pointed out, start conversion and any necessary hardware mods that may be required. If its a digital pin than of course you will only be able to 'read' voltages that are with the logic high and low voltage levels. If you want to start off with PIC ADCs than i would recommend this document to get familiar with the jargon