OK so first you will need to win the Master Rank of the Pokemon Contest to one Pokemon then talk to the painter and it will be in the museum.
Chat with our AI personalities
Take it to the museum in Nacrene City
you probably forgot to go to the dragon helix tower, after that the ancient castle and after that the shippou city museum.
Do you mean Archen? You can revive it in the museum from a fossil you get from a man in the Relic Castle. You can chose between this fossil and another one.
Dock is located at the Shipyard in Slateport City. You must talk to him in order for the Team Aqua/Magma grunts to move, allowing you access into the Oceanic Museum.
You don't get Deoxys from anyone in the mining museum You have to trade it from Diamond/Pearl, or migrate it from Ruby/sapphire/emerald if you went to any of the events.