Top two pieces go on the top of the sill panel, visible when you open the door. They hold the edge of the carpet to the inner sill panel so that it looks tidy. Bottom left would be the same for the rear door, and bottom right would be for the base of the B pillar (I think its B pillar in between the two doors right?)

Personally I think these metal ones looks a bit average. I wouldn't mind finding a plastic substitute from a donor car to replace them...