I usually use them on an insert on the monitor end (don't track the dolby), although if you like the sound of it while tracking, why not print it!
You need to send your signal to the encode end of the unit and then out before the decode... I think the input is labeled: "line in" and the output is labeled "to record"(or something like that), and then just make sure the "in" and "rec" buttons are pushed in on the front panel.