spdif/sound recording

i recently bought a toneport for guitar recording. it has an spdif output and would like to use it on an imac. i recently checked the stores to see if imacs have that spdif input but did not have any. i asked the guy who worked at the apple store and he didnt know what i was talking about.

my toneport also has a normal audio out. im interested in using imacs for recording. can anyone tell me if these are compatible?

i was playing around with garage band as well and i liked it a lot