If you have Leliana's Song for Dragon Age: Origins
, earning this trophy is easy. Unlike in the main game, you won't need to learn any specializations; the characters in your party will all have at least two unlocked.
Simply start a new game in Leliana's Song. Your character should start with a level up pending. Finish the leveling-up for one character. This trophy should pop after you've finished leveling them up, even though they started with the specialization already unlocked.