As you level up with your champions in Mythic Victory Arena you are given the option to unlock a skill after each level up. With this DLC you can have all skills granted to you by default without having to level up your characters. However, you still have purchase the skills to be able to use them.

Visit the Skill Shop to have all your skills unlocked if you're loading up a saved game.

Get out there and beat 'em down with your flashy finesse.