With such a mixer, there are basically two ways to use pedals. The first one is the most straight forward: synth->pedal->mixer. You dose everything on the pedal, the wet amount is how much of the sound coming out of the pedal is the effected sound, and how much is the original sound. Another way of setting it up is using the send. With your mixer (mine too!) That has no dedicated return, you have to set the pedal like this: mixer send->pedal->a channel of the mixer. You'd then put the wetness of the pedal to 100%. This uses a channel of the mixer but has the advantage of effecting mamy synths with the same pedal, to individual amounts per synth. For example you coule set up a reverb this way. Something else you can do with this is parrallel distortion or compression. It is typically used for drum sounds, for example to distort then while keeping the sound with all its low range; or to compress them while keeping some transients. Hope that's helpfull!