Put it last in your chain and slowly start to move the knob against the 'Default' position. A good blanaced mix/master should survive all the way to 'Default' with just a little increase in harshness. If you find your mix too harsh halfway through you'll have to go back to the mix/master and use EQ, MB compression or other tools to soften it a bit.
Remember to put the plugin at 'Flat', bypass it or remove it before bounce your new mix/master.
You only need this if your mixes/masters are too harsh when played outside of your studio. If that's not the case this method might cause more damage than good to your tracks.