Logic Express Trouble, recording Options

[kwantus]

I have recently got logic express after using garageband for a while and know abit about it from online lessons.
But i cant get my guitar plugged into my M-audio fasttrack interface to work! Every time I try it gives me 2 input settings and both when selected use the computer inbuilt mic to record.
Ive changed all he system prefs to fast track and it works on garageband but is just not recognised by Logic is it something to do with it being usb powered?
Can someone pleaaasseee help!
Cheers,
Tim