you really just need to plug the output of the M/disc player into an audio interface
if you don't have a sound card (audio interface) that you use with your mac you can get cable to plug into the headphone port to record the output
i recommend that you leave a couple of seconds at the beginning and at the end of each track so that you make sure all of it gets recorded so start recording before you start playback of your speech tracks.
by the way, if you want to do recording more frequently i would recommend that you buy a proper usb audio interface. There are relatively inexpensive models that contain much higher quality converters than the built in converters of your iMac's headphone/microphone port
let me know if you have any other questions!
be well,
-Sean