Asking about Skill on weapon (Help please)

[omniversal]

I wanna ask how to make skill or spell like Frost nova or other spell in the weapon to attack passively ??
example : Every Time You attack with Divine rapier the weapon will passively or automatically cast Frost nova ( i put Frost nova ability to Divine Rapier to Hoping that everytime i attack it will automatically or passively cast Frost nova But i failed)

If you ever play "Bleach versus Onepiece 2.08b" You can see The weapon like Frostmourne in the level 6 shop ( That weapon everytime you attack it will automatically cast Frost nova)

Can anyone help me if it needed Trigger please give me the GUI Trigger THX !! With the easiest way