The mannequin system will be part of the UI. You won't have to "take" them anywhere because it's not something that goes in your inventory.

Think of the equipment screen we have in XIV right now. Now think of having a bunch of those, one for each class or job, that you can switch between at the click of a button. Now think of all that equipment not taking up space in your inventory. That's what the mannequin system will be like.