The thrust bearing (3) attaches to end (1) of your ball screw and is fastened with locknut (6). This bearing is the critcal bearing as it establishes the orientation of the ball screw. In other words, you assemble and mount these first and align the screw with the axis for parallelism (veritcal and horizontal)
The couping (8) goes between your motor and the ball screw on the thrust bearing end of the screw(1). Again, do you best to align the motor so that its rotational centerline is the same as your screw.
The end support bearing(5) fits in housing(4) and snap ring(7) retains the bearing on the end of the screw. When securing this bearing housing, you have to make sure that the ball screw is parallel vertically and horizontally to the axis.
8 -> 6 -> 3 -> 1 -> 2 -> 5 -> 4 -> 7
That should do it for you