how to drain transmission fluid of a mazda 323? i check the dip stick and i

cant really tell the level.? all i can see with dip stick is a red foamy substance. is it a sign that it is over filled? i poured in 1 liter yesterday coz its kinda hard for the car to move and i thought it doen't have enough fluid to work with.
its an automatic transmission by the way.
and how many liters does the tranny needs?