I am guessing you mean the Dark Legends on iOS? (I'm on Mobile app)

If so Tapjoy was disabled for the iOS client a few weeks back. We have not had any news since. There are video offers that get you platinum in the iOS client now, but no downloading/getting the platinum process for the time being.

Alternately, you can go to Tapjoy's website or email them. (Email address will probably be on website). Create an account on the website and search for Dark Legends and like them. Then click "free offers".

Please note that the "Free Platinum" feature is not available in the chrome version of the game.