Need help in Devil May Cry 3(special edition)?

i've recently got hand 2 Devil May Cry 3(special edition):Dante's Awakening.i've crossed 4 stages &defeated th joker in 5th one. After this i again reach th chamber of echoes and insert th astro.something.now i get an ornament. the circle on the ground highlights and becomes a launcher. now i have nothing 2 do. how can i go furthur. please help.