Play Framework Checkbox and duplicated Entry

I have in my Scala View a for loop that displays an all saved records of an Entity as checkboxes inputs, so I have N numbers of checkboxes. The idea is to map that Entities with another with ManyToMany annotation.

I could display the checkboxes and can persist the data. The issue is that any checkbox that i check is save as a new entity and not mapped with the current saved record that exist.

I really do not know how to change this, every time that I check on checkbox I have a new Entity and my father Entity (what has the ManyToMany annotation) is mapped with the a new persist entry.

Can you help me please?

Thanks & Regards,