Make sure that the pump's brusholder is in the correct position, like in the first picture. You should have the cables looking down on the right and the MARCO logo in the sticker on the stator that looks toward pump's head.

Insert the pump's head tie-rods in the holes between the magnets.

Push the tie-rods down to the end of the motor: they should come out on the other side, as seen in the next steps.