The redeye 3d has 2 inputs. the Active input on the front. It requires phantom power. Or the passive input on the back. It does not require phantom power.
If you have active pickups in your guitar, plug into the back passive input. If you have passive pickups in your guitar, plug into the front active input.
Run an instrument cable from the intrument/ reamp out on the front of the redeye to your amp.
run an xlr from the 'mic level out' on the back of the redeye to your interface. Remember to engage the phantom power on your interface if you're using the front active input of the redeye.
The DI/Reamp button should NOT be pressed if you're using it as a DI. Done.