[RMMZ] USING ITEMS AS SKILL COSTS

I'm trying to add a class to my game that's similar to the "Salve-Maker" class in Bravely Default, which is one that possesses skills that require items to use instead of MP or stuff like that, but I'm having trouble understanding how that works with the SkillStates plugin I have.
Does anyone have any idea how setting items as a skill cost works?