I have no experience with that particular pedal , but there are some general rules I like to apply when trying a new pedal :

Heavy Metal:
Gain: pretty high
Bass: over 5
Middle: below 5
Trebble: below 5 but higher than mids


Classic Rock:
Gain : Lower than heavy metal (you should be able to play a full chord, say Emin and be able to hear all notes clearly)
Bass : over 5
Middle : over 5
Trebble : below 5