The makeup kit is an accessory that gives you additional hair color and skin color options to choose from when customizing your character's appearance. It does not take up a slot in the Accessories bar.
How to Obtain
The only way to obtain this item is to purchase it from the crown store. It cannot be traded.
How to Use
Merely purchasing this item will activate it; you do not need to put it in the Accessories Bar. To change your hair or skin color, go to your profile and choose "Appearance." You will see the new options there.