How do you get an azure flute in friend?

How do you get an azure flute in friend?
After you get dialga/palkia and some cool Pokemon go to any pokemart and talk to the guy in green.He'll give you the flute. Then head back to where you fought dialga/palkia. Enter the spear pillar but don't go up the stairs. Instead,blow the flute in front of the stairs and it will open a new staircase. Head up the stairs and you'll see arceus. There you can catch or faint arceus.But you must capture it with a master ball. If you used it for garitina use a preimer ball instead. Making it faint is a bad idea. Make sure its health is red so that you can capture it. If it doesn't work the first time with a preimer ball or master ball you must make it faint or use a different poke ball. You meet arceus in LV.80. If you have garintina [which is a LV.70 when you meet it]make sure its LV.81 or higher. Once you have a arceus on the pokedex it says '' it formed the world with its 1,000 legs''but when you look at it it seems to have 4 legs. Maybe its invisible.