Obtained: Speak with Fortuneteller Baba at the World Tournament Area in the Far Southern Islands Area during the post game as Goku. *NOTE: I completed every other Goku story I had in order to get it to show up.
Objective: Talk to Baba about training
Travel to the World Tournament Area to find Baba near the entrance of the arena. Speak with her to trigger a cutscene then head to the Land of the Kais to face your opponent. Defeat the fighter to complete the story.