where do I start to change the transmission fluid in my 2002 pontaic grand am se 2.2 dohc

Just like engine oil, you have to start by emptying the fluid from the trans. Not sure how a Grand AM trans is designed, but if there is no drain plug on the trans casing, you will either need to suck the fluid out via the fill tube or drop the pan on the trans casing. Then reverse what ever you do and refill. There is typically an internal filter that could be changed if you drop the casing to drain the unit. Good idea to change that when you have it apart but unless you have major miles on this trans it could probably be left alone.