I don't know Mixcraft, but you'll probably have to add tracks to the project and assign hardware inputs to respective tracks, then arm the tracks. You may need to select the correct driver in the preferences.
I prefer to record at 24 bit and 48kHz. At that quality it will use about half a gigabyte per track per hour.
I would plan to spend some time ahead of the gig connecting and troubleshooting the setup.
Look into optimizing a PC for recording. Usually the first thing suggested is to disable the wireless.