To adjust the current trigger you simply remove the trigger gaurd and with a very small flat head screw driver turn the screw located in front of the trigger either clockwise or anti clockwise to to tighten or loosen the trigger.
Be careful turning that little screw on the back of the trigger, the heads break off easy. You won't break it as long as you don't get rammy. Speaking from experience here.
You usually can't get the trigger set low enough with the adjustment alone but installing the light spring from the timiney trigger kit will make all the difference. Its a fairly easy do it yourself job too.