Just went through the same situation earlier this year. This was my procedure.
The first exercise is to lay out each outer and inner piece piece noting the "curled" edge and somewhat straight side of the cross section of the stainless.
I had my whiskers, and channels installed and windows in working order before installing the stainless, especially, since my "wing window was out and must be fully seated (forward) for everything to work properly and the stainless to mount properly. I left the inner door panels off.
OUTSIDE:
I started with the front wing forward piece. Next, the back side of the wing window - it will be under the top piece ever so slightly. Then, I went to the back of the door and snapped it on. Next was the top of the door where the top piece must abut the front wing piece and the rear piece. It may take the gentle taping of a rubber hammer to slide a piece in position. The final piece is at the bottom of the window and has "cut-outs" to cover the three vertical pieces.
INSIDE:
The front wing, forward goes on first. Obviously, the very small screws will align where the front goes and where the top goes. The wing pieces fit slightly behind the door panels. The back piece has a small screw at bottom and partially behind door card. The back piece of the wing window snaps in last.
The stainless will snap on rather easily if the inner channels are not bent.