The ammonia needs to be a solution of just ammonium hydroxide in water - no soap, detergent or perfume. I know a lot of Americans use ammonia from Ace Hardware if you have one near you. Failing that, try Amazon or Ebay.
In the 'how to tips' at the top of the page, there is a calculator and the last item in that is a calculator to work out how much ammonia you need to add. A syringe can be useful for measuring accurately. I get my syringes from a pharmacy (drug store?) but I always ask for babies' medicine dosing syringes as asking for just a syringe could result in some personal questions
If you could find where your water comes from it would help. Do you pay someone to provide your water - if you do, their contact details should be on a bill. If there is no website, phone them.
As a rough guide, do your shower head and kettle fur up? That is a sign of hard water.
The API test kit is the one I use. Test both your tap water as well as tank water, the tap water will give you a baseline to work from. With pH, test some freshly run tap water and also a glass of water that's been allowed to stand overnight. You'll probably find they are different.
With the nitrate tester, bottle #2 says to shake it before adding to the test tube, then shake the test tube. This shaking is necessary because one of the reagents settles on the bottom so it needs to be mixed back in. With a new bottle, or one that hasn't been used for a while, tap it on the worktop a few times first to break up any large lumps.