Recording guitar via USB with Digitech RP255

i foolishly assumed that buying this $150 product would enable met to easily start recording the minute i took it out of the box and loaded up garageband. 'twas not to be. since it is 2010 and we're cloning sheep and such, i know there has to be a way to use this in GB. could someone who has used this product perhaps list how i need to configure my settings in GB to make this happen? thanks and much appreciated!