How many fishes do you have? Do you have proper filtration? Please give us specific details. Try doing a 50% water change every day for a few days, that should help bring down the Ammonia.
If you added too many fishes at the same time, at once, in a new cycling tank, there is no good bacterias established yet to convert Ammonia to Nitrite to Nitrate. It takes time for the tank to be established, so I advise only adding very few fishes for cycle or do a fishless cycle. Cycling with a fish will establish your tank faster, but you do not need too many fishes at the same time. So, do constant water changes to keep the water conditions in check until the cycle has completed.
Thunder