Did you play football for Notre Dame.<g>
Seriously, to change power steering fluid, disconnect the lines at the power steering box. and drain. Reconnect the lines, and fill with power steering fluid. If you don't want to get it from your dealer, power steering fluid from the auto supply works okay. ATF is not reccommended for this application any more, the additives have changed over the years, it's now not good for the seals.
After draining, and reconnecting the hoses, fill the reservoir, start the engine, and turn the steering wheel lock to lock several times to bleed out the air.
To get a thorough flushing, you may have to repeat this procedure several times. The fluid is cheap and it's worth having clean fluid in the system.
There may be a plug on the underside of your steering box which would allow you to also drain the complete steering box.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
Over 800,000 miles in