Use model of diiferent name in a different controller

I have a controller FormsController and a Active Model ApplicationForm. I have made this model by including include ActiveModel::Validations, include ActiveModel::Conversion, extend ActiveModel::Naming. When I'm using @form=ApplicationForm I'm getting NameError uninitialized constant FormsController::ApplicationForm. How do I resolve this issue, I just want to use this Model as class which can provide object to hold form values temporarily for further processing.