Ok hon, calm down, deep breaths. To do a water change, unplug the heater and the filter if its an internal filter, if its external thats fine leave it running, but definatley unplug the heater.
Get a bucket and use something to take some water out, a cup if you need to, change about 3 buckets full of water - tip the dirty water down the drain. The re-fill the bucket with fresh dechlorinated water (you can add warm water from the tap to get the temp right) and slowly put the water from the bucket back into the tank.
Once you have finished, turn back on the heater and filter if you turned it off.
Just take your time and dont rush it.
For your water stats, dont worry for now, although its easier to work out what is happening with a test kit, you can always take a sample of the water to the LFS and ask them to test it for you - get them to right down the results.
However, the problem is probably ammonia and nitrIte poisoning and for this you need to do regular water changes, its the only way to get the water quality right for the fish.