The arms ("window regulator" mechanism) that make the window go up and down need to be removed by releasing the rollers from the window's frame.
There will be three rollers for each window. Pull the little wire clips, and then the rollers can be removed from the pins on the window regulator arms. Then you can pull the whole device out the large opening at the bottom of the door.
Consider throwing away your old rollers and replacing with solid brass units (especially for the rear quarter windows). They are available now through another member here on this site.
I did all this window work back in the winter of 2009-2010, and if I could do it back then when I was a newbie with these old cars, you can do it too.