Go to the DW, play until youhave 10,000 points (you get roughtly 200~500 a day depending on luck and skill).
Once you have 10,000 points, keep playing until you find a Dratini with Marvel scale in the sparkling sea area. Level it up to dragonite and hope when it hits that point you get the hidden ability andnot the normal one.
Alternately get one from a person who has already unlocked this (mostly Japanese only) in their game..and/or someone who has bred them from female DW pokemon. --- Reviewer and news gaming sites are only credible if it proves the poster's point. If it doesn't, then they're just biased trash. -- Savott on Troll thinking.