First you have to have an insert type cable (stereo 1/4" on one end that fans out to two mono 1/4", one connected to the pin of the stereo end, the other to the ring). The stereo end goes to the INSERT on the mixer/preamp the other ends go to the IN and OUT of the device you want to insert. You have to check your documentation of the mixer/preamp for the pinout to determine which is send and which one is recieve on the insert. Failing that hook it up and see if it works. If it doesn't, reverse them and it should.