Where do you add transmission fluid in a 2000 Malibu?

Well, unfortunatly you don't. You take it in, and they can do a flush as the only access point to the fluid is underneath the car. If you are concerned about the fluid level and it has been 33,000 miles since last fluid flush take it in and have it flushed. There they have a machince that sucks out the old fluid and puts new in.