i was testing my water and the ph was really high. how can i make it lower ??

What kind of fish are in there? Some tropicals can handle quite high pH, as long as it is stable. You might not have to change the pH at all, depending on what kind of tropicals you got....

i hav neon tetras, cardinal tetras and guppies

How high is high and how long has it been high. Does the fish show any sign of distress. Do you have readings for ammonia and nitrIte as well?
What is the pH of your source water?

its ph 9. da anomia and nitrate tests were fine. da tetras are fine but one of ma gupies died da ova day but the other guppies probs killed him not da water cuz they evil .... lol

someone told me to boil da water wen i do a water change. will this help ?

Can you please test the tap water pH. I won't boil the water as it will change the water chemistry you might just open up a new set of problems.

Has it always been high or was there a recent dramatic spike in it?