Assign form to content type

Options allow for creation of new form, I'd like to assign an already existing form to a content type. I have a gallery with hundreds of items. I'd like one field to be hidden and post %parent-node i.e. name of associated node. There there's normal fields like name, address, telephone. I get their details and know which node they are referring to. Is not possible to create new forms for each gallery item.

If anyone knows how this could be done please let me know.