The game is currently available in the the Google Play Store and the Chrome app store; it won't be available in the iOS app store for a few more weeks. Like previous offerings, it's free-to-play, and you can log in from separate devices to play both on the road and at home. Unlike previous games, this one is definitely not aiming for the family market, being a fair bit more overtly violent and bloody. Still, if you feel the urge to rampage through dark alleys while you are walking through said alleys in real life, Dark Legends has you covered.
[Update: We've clarified that the game is not yet available for Apple users. Sorry for the confusion!]