Weekly water changes of 50%. Since you have ammonia, you need to get it down to 0. Do 75% water change daily until it reads 0. Test daily until you are at 0. Then do the weekly 50%.
Add prime to the new water that you're putting back in the tank. Make sure it's the same temp. If you do this, you should be able to get the ammonia down. Don't overfeed. In fact don't feed your fish for a couple of days. Also, do a good gravel vac each week too.