Hi Chris,
I found you can set it up a few ways;
The way I did it was turn the screw on the pressure relief valve all the way in. Then use the dial on the radio to adjust the constant pressure, which will be only about half way. Mix off on radio with this way. (the toggle switch on right move to lower position) I like this set up as I can tweak the function speed/power on the fly.
Second was is to open the pressure dial up..screw it out then mix is "on" (toggle flip up)and turn dial all the way up on the radio (it controls the 4th servo/valve on hydraulic block)
For even more tips on mixing radio functions and just about everything else you will find the guys on this forum really know their stuff and you will get the right answers to almost any question
Hope that helps!
Tom