uh... you step on the pedal - make the switch go "click" and then you move your foot back and forth... make sure it's plugged in the right way and the battery is good - it's not rocket surgery.
oh yeah - forward is more trebly - - back is bass-ier
seriously though
to me the "wocka wocka" sound comes from hitting the strings without really playing a note - just muting it or holding the strings and moving the pedal
try synch'ing up your picking and your foot motion
try using it as a sweep - moving the pedal very slowly as you play
if we could hear what you were doing maybe we could help more
here's something a I did a while ago that features the wah wah - - yeah it's cheesy:
http://www.soundclick.com/bands/page_songInfo.cfm?bandID=795734&songID=6185321
other tracks with wah wah:
http://www.soundclick.com/bands/page_songInfo.cfm?bandID=795734&songID=6196576
http://www.soundclick.com/bands/page_songInfo.cfm?bandID=795734&songID=6216726
http://www.soundclick.com/bands/page_songInfo.cfm?bandID=795734&songID=6194058