Line 6 pod xt

Is it best to connect it to the imac via S/PDIF?? Other than the free Garage band I haven't bought a DAW software yet.
 
I'm having no luck making this thing work.. where should i plug the input jack from the left output (of the pod) into the firebox (mic 1/line in or line out?) There's just no sound coming out whatever I do.. help please!