You hook up the ground to the ground of the robot, not to the relay, then you put the two wires on the relay, which one doesn't really matter, when you push the button to activate it, you'll have to hold it down, unless you alter the programming to make it like a double solenoid works. If that isn't working maybe you put it together wrong, search the forums and you'll find a link to the pdf of how to put it together
a matter of fact I have it on my server
Festo Valve Assembly