I believe you can, however I havent done it yet. I know I've read a thread on here that had a video explaining how to do it, might be best off searching for that.
This should be quite simple. Any audio is sent out through the USB port. So If the Fantom G driver is correctly installed on you PC, .the signal should arrive in your DAW if you select Fantom as audio interface there.. At least it does with Cubase... Make sure to have set the correct input source (MIC oder LINE - not USB!) to record external sources.