Hello,
You need to define a Hibernate mapping of the many to many association to a table structure. If you are unsing Hibernate annotations, this documentation should help :
http://docs.jboss.org/hibernate/annotations/3.5/reference/en/html/entity.html#entity-mapping-associationIf you are using hbm.cfg.xml see this section of the tutorial in the Hibernate reference docs, if you are new to Hibernate it would probably be worth you reading the whole tutorial section.
http://docs.jboss.org/hibernate/core/3.5/reference/en/html_single/#tutorial-associations-unidirsetand
http://docs.jboss.org/hibernate/core/3.5/reference/en/html_single/#collections-ofvaluesThat should provide you with what you need to get started,
Kate.