Delmatt, I'll try to do my best here.
At the back of your DP01 unit there are 3 female 1/4 terminals. One is "effects send" and the other two are "effects return" (this can be stereo or mono, if the return signal of your effects device is in stereo, then plug both L & R, if not, just plug the L (mono)).
Plug your effects send cable to your effects device "in" , and your effects return cable (s) to the effects device "out".
In each track you have a knob that says "effect send", this controls the signal that's going to be processed by your effects device. And there's only one knob, at your mixer's far right that says "effect return". This knob regulates the amount of effect that is going to be heard in your final mix.
Hope this helps a bit.
Cheers!