You need to activate the mistery gift then save and turn the game of and on then go tho mistery gift before you open the saved data . when you openen the mistery gift there wil aper agan mistery gift go there two then there wil be 3options take the last 1 at the data when there wil be an arceus event , make shure thet you got wi-fi conection. If you got the event go to any pokemarkt ant talk to a man in the green suit and you gat a azure flut then go to sper pillar there wil a mistirios stars aper go up and you wil see an arceus