add new property

Hello! I'm trying to add other properties when one creates a part but I do not find the way to do that. I mean when an user creates a new part, I would like he could complete more fields than "Part number", "Name", "Type", "Cost", etc. For example he could complete a new field called "Model" or "Location". I tried to do that by creating a new property in the itemtype part without ticking the "hidden" case but it did not work. If someone could help me ! Thanks !