Paperclip update user table entry with existing image

I have a form that uploads pictures and keeps the old ones there:

<%= form_for(resource, as: resource_name, url: registration_path(resource_name), html: {:multipart => true }) do |f| %>
 <div class="form-group">
  <label for = 'file-upload', class='btn btn-large btn-block btn-info'>
  <span class="glyphicon glyphicon-upload" aria-hidden="true"></span> Upload Picture
  <%= f.file_field :image, id: "file-upload", onchange: "this.form.submit()" %>
</label>
</div>
<% end %>

I am retrieving the uploaded images in my devise registration controller:

   def edit
    @images = Dir.glob("public/assets/images/users/#{current_user.id}/med/*")
  end

I am generating an array of image paths for the current user in my view:

<% img_paths = Array.new %>
<% @images.each do |image| %>
<%img_paths.push("/assets/images/users/#{current_user.id}/original/#{image.split('/').last}")%>
<% end %>

I would like to select one fo these paths and update the user record with the new image details with something like this:

<%= form_for(resource, as: resource_name, url: registration_path(resource_name), html: {method: :put }) do |f| %>
<%=f.select(:image, options_for_select(img_paths))%>
paperclip.update_current_image_with_my_new_image_from_img_path_url 
<%end%>