connect the effect send 2 output to the external effects unit input, connect the effect unit output to an input channel on the DP24, assign the input channel to a track, use the effect send 2 level to adjust the amount of dry signal sent to the effects unit, tweak the parameter settings and output level on the effects unit and then set the input trim, etc on your DP input channel. arm the track and record. you can later mix the original vocal track with the wet track if desired. I think that sums it up.