I think, here you will find your answer: https://github.com/plataformatec/devise/tree/rails4#strong-parameters
Based on above link, I think you should insert something like this in your ApplicationController:
class ApplicationController < ActionController::Base
before_filter :configure_permitted_parameters, if: :devise_controller?
protected
def configure_permitted_parameters
devise_parameter_sanitizer.for(:user) { |u| u.permit(:profile_name) }
end
end
And I already suggested in a previous question... Strong parameters with Rails and Devise
...that you can create your own controller which could extend devise own controller. There is a gist for that: https://gist.github.com/bluemont/e304e65e7e15d77d3cb9
A little bit more details in Devise doc: https://github.com/plataformatec/devise/tree/rails4#configuring-controllers