When connected to the computer with the DAW the ZED will show up as an audio interface option.
Connect you guitar inputs to the mixer as you would any other analog mixer.
For a simple straight up stereo recording to your DAW have both of the push button switches under the USB connector in the up position, doing that will send
the same signal that is coming out of the stereo outputs on the mixer into the DAW
for recording.
I have a ZED 10 (same mixer with no FX) and I use it as much for a computer IO as I do
for just a small utility mixer.