Replacing Rear Shock

1990 325ic and I have the Haynes and Bentley manuals and all indicate I muist remove the two (left and right) support bracket nuts in oreder to drop the shock out. I thought that taking the center nut that threads on the piston rod would drop the shock out (not true)? If taking the nuts off will that drop the shock? and what abot ther center nut on the piston, when does that come off and go back on? Kids car and I am really confused, eager to go to work, but confused.