[Zope] creating an instance of your own product within Python Scripts

Hi, What do I've to accomplish to call context.documents.manage_addProduct['OFSP'].manage_addFolder(id='new_id2') with my own product? eg: context.documents.manage_addProduct['OFSP'].manage_addCasusDocument(id='new_ id2') I've already made it possible to import manage_addCasusDocument through python scripts. However now I'm stuck and don't know how I can create an instance of my product inside a BTree folder Thanks in advance, Tom.