Behringer Uca222 Problem

Hi,I just got a behringer uca222 sound card to record directly from my behringer 802 desk onto my macbook. I have both garageband and audacity to choose from as my audio editing programme. When the uca222 was delivered it did not come with the cd rom with any software on it.I have connected it to my desk using dual rca cables from both the input and output, as I have chosen to hear playback through headphones rather than speakers.I have connected my headphones to the uca222 but when i try and sing or do anything from my mic, it's only when i make a particularly loud noise that anything comes out of the headphones (all i hear is distorted kind of noise), and nothing reaches Audacity - it's just recording silence despite recognising the uca222 and me selecting it as the input mode. I also have the volume on the desk and uca222 turned up.The 802 desk is designed to be used with powered speakers as it doesnt have much power itself. I don't have powered speakers so when I use the desk with a PA I run the mixing desk through an amp and then into the speakers. Does this have any impact on my situation? Will I need to run the desk through the amp and then into the uca222 rather than speakers in order to hear anything through the headphones? Or are any of the various ASIO drivers and plug-ins that come on the cd rom which I didn't receive what I need?Thanks,Sian