This can be done during the tutorial with
Sora. The tutorial makes you pick up a crate using
, from here you can just toss it at the
Shadow that appears in front of you.
If you missed , that's fine, there are several other objects within every single room in the game. They are the barrels and the crates with the stars on them.
Once you make contact with an enemy from an item you've thrown, the trophy
Ace Striker should unlock.