To unlock the Epic Talent trophy in Anthem, you will need to increase the Gear Score of one of your Javelin's until it reaches the Epic (purple) level. The Gear Score required is 395. The overall Javelin's level must be Epic.
The gear score is an average of all of your gear. The higher the score, the higher the rarity. Once you have reached the Epic level with a Javelin, complete a mission, contract, or stronghold and the trophy will unlock at the end.