You would just run the effects loop send to the tuner input, then from the tuner to anything else in the loop and back to the return. However, there is a caveat.
The Pitchblack, like most pedals (and especially most tuners) isn't really meant to be placed in an effects loop. Effects loops are line level (read: AMPLIFIED) and pedals are generally meant for instrument level. Therefore, the Pitchblack ideally should be either between your instrument and amp, or plugged into the amp's tuner out. That isn't to say that you CAN'T use a pedal like the Pitchblack in the effects loop, but don't blame me if the line level input blows it up.
Hope that helps.
