According to the positional relationship among light screen, convex lens and candle flame, the center of light screen is higher than that of convex lens and candle flame. To make the image in the center of the screen, it is necessary to adjust the screen downward so that the centers of the three are at the same height.
Object distance 15cm, convex lens focal length 10cm, object distance greater than one focal length but less than two focal lengths. According to the imaging law of convex lens, the object becomes an inverted magnified real image on the light screen.
So, the answer is: below; Zoom in.