Do you have an insert jack on your 003?
Typically you run a tip ring sleeve 1/4 inch cable into the insert.
The send is on the tip and the return is on the ring and sleeve is on the ground.
Check the back of your 003 for inserts on your mic pre.
You also need an insert cable, or make one yourself. They are very basic, I've made a bunch for my studio and saved $$