Fields for Avatar upload using carrierwave

_login_forms.html.erb

<div class="collapse" id="register">

            <%= form_for(resource, :class => "collapse", :html => { :id => "registerForm", :multipart => true }, :as => resource_name, :url => registration_path(resource_name)) do |f| %>
                <%= devise_error_messages! %>

                <!--[if lt IE 9]>
                <label for="user_password">Enter email</label>
                <![endif]-->
                <%= f.email_field :email, :autofocus => true, :id => 'signup_email', :name => 'user[email]', :placeholder => "you@example.com" %>
                <!--[if lt IE 9]>
                <label for="user_password">Enter password</label>
                <![endif]-->
                <%= f.password_field :password, :id => 'signup_password', :name => 'user[password]', :placeholder => "password" %>
                <!--[if lt IE 9]>
                <label for="user_password">Confirm password</label>
                <![endif]-->
                <%= f.password_field :password_confirmation, :id => 'signup_password_confirmation', :placeholder => 'confirm password' %>
                <!--[if lt IE 9]>
                <label>My Avatar</label>
                <![endif]-->

                <%= f.file_field :avatar, :placeholder => 'your avatar' %>
                <%= f.hidden_field :avatar_cache %>

                <div><%= f.submit "Sign up", :id => 'signup', :class => "btn btn-primary" %></div>
            <% end %>
          </div>

new.html.erb

<section id="devise">
<h2>Sign up</h2>

<%= simple_form_for(resource, :as => resource_name, :url => registration_path(resource_name), :input_html => {:multipart => true}) do |f| %>
  <%= f.error_notification %>

  <div class="form-inputs">
    <%= f.input :email, :required => true, :autofocus => true %>
    <%= f.input :password, :required => true %>
    <%= f.input :password_confirmation, :required => true %>
    <%  if @user.avatar.url.present? %>
        <%= image_tag(@user.avatar_url.to_s) %>
    <% end %>
    <%= f.file_field :avatar, :placeholder => 'your avatar' %>
    <%= f.hidden_field :avatar_cache %>
  </div>

  <div class="form-actions">
    <%= f.button :submit, "Sign up" %>
  </div>
<% end %>

<%= render "devise/shared/links" %>

</section>

https://github.com/carrierwaveuploader/carrierwave