How do you change the transmission fluid on a 1996 Chevrolet Cavalier Z24?

If the transmission has a drain plug in the pan, remove the plug, allow to drain for at least 1/2 hour, so that the torque converter will drain, replace the plug, add fluid, run engine, put transmission in drive, neutral, reverse, neutral, drive, repeat for about 5 minutes, check fluid level, top off if needed, repeat running in drive, neutral, reverse. If the transmission does not have a drain, you have to drop the pan, which is best done by a transmission shop.