Yhe are in several areas along the route, just ask a cast member. There is one in Librety Square, one opposite Tomorrowland..and a few others. You may want to get a spot as soon as you see them setting up for the parade If you get a spot early enough, you can also get a good spot outside the designated areas.
Remember though, they usually have two "rows"...and able bodied companions are allowed in also. If you are in the back, you may need to remind someone standing in front of you that you are there, if they are blocking your view. We went to the parade twice. First time no problems..second time I had to politly ask a woman to move several times as she kept steping directly in front of us to take pictures. Finally her hubby (in a chair)noticed our frustration, took her arm and said, "No more pictures, you are blocking their view"