The three tiles that are on the first row next to each other are from left to right: white dress, red dress, blue dress. The two tiles that are in the second row are from left to right: salesman, Lana.
This is because according to the stage directions the blue dress is on the right of the stage, the red one is in the middle (downstage) and left of the blue one according to Lana, and the white dress is beside the salesman, so on the left of the stage. The salesman is on the left next to the white dress so Lana has to be in the last tile that remains blank ,because the dresses are all in front of her according to the stage directions and she can't be on the left tile of the second row because the salesman has to be there.
