Guess others could tell you how to change it...  but what I do is take my
'new used' cars to a 'name brand' location like Pennzoil & have them
connect their transmission flush machine.  This has worked good for me for
the past six years or so.  Supposedly it also changes the fluid that is
normally trapped in the converter that does not come out when you change
the fluid yourself.

This saved a rebuild on an old Ford pickup that had been very slow to
shift between 2nd & 3rd.  It has been over two years now & still shifting
good.

The cost here in North Texas is about $65.