Now you need access to your basement or crawl space, if the bathtub is on the second floor there should be an access panel in an adjourning closet. I was able to get access through the basement.

As you follow the drain from the tub the first joint connector needs to be loosened counter-clockwise.

If needed, use a pair of pliers can get you started. Be careful, the plastic is soft and can crack if too much force is used. When you remove the drain pipe, the bathtub drain will be exposed. Now we need to try and take care of the rust around the drain flange.