Hi mate, i have a Fantom G, install the drivers and use USB (MIDI) instead of the 'old school' MIDI ports, will suit what you're trying to achieve much better.
Yes, it functions as a midi keyboard, but when you have it connected via USB you can have audio going direct to your computer and back PLUS use it as a midi keyboard.
MIDI, if you're unaware is basically a series of messages that tells your computer when a note has been pressed, which note it is, and when it's been released. So when you're recording MIDI data, no sounds have been recorded. However, when you play that recorded MIDI data back, it will trigger your Fantom to play exactly how you originally recorded.
But it will playback out of your Fantom's line outs/headphone ports.
You either need to connect a cable from those ports into your computer... OR, as already stated, use the USB port, install the USB Audio driver and you're golden mate!
As the Fantom is multi-timbral (i.e. you can use many different sounds at once) then you will need to look into MIDI Channel numbers and setting up your Logic tracks to correspond with what sounds you have loaded on which channels. But one step at a time! 🙂