从选择框中获取数据并将其传递给params

I am doing this for a school project and it is not working. :( How do I get out the selected[petowner_id] from the view and make it usable in a ruby controller? How do I make the @selected_pet = params([petowner_id]) in the controller that comes in from the view to function? Currently it renders an error message when I try to set it. :( I am getting very tired of it not working.I am doing this for a school project and it is