Routing a resource to controller - ruby-on-rails

Question

How do you route a resource to its controller? I am using the resource in an edit page for a different model, so my actions are being routed to its model controller first.
This edit page requests from
class Grandstreamers::ResellersController < ApplicationController
def new
end etc...
I am trying to route the requests to here instead:
Grandstreamers::CertificatesController < ApplicationController
def new
end
def update
end etc...
This is my form under views/grandstreamers/resellers/edit.html.erb
<%= form_for #untrained, :url => certificates_update_path(#untrained) do |f| %>
<p> Trained Users </p>
<%= select_tag "certificate[user_id]", options_for_select(#current_trained.collect{|x| [x.name, x.id]}), {:multiple => :multiple} %>
<%= f.submit "Un-Train", class: "btn btn-large btn-primary" %>
<% end %>
<%= form_for #trained, :url => certificates_create_path(#trained) do |f| %>
<p> Non-Trained Users </p>
<%= select_tag "certificate[user_id]", options_for_select(#non_trained.collect{|x| [x.name, x.id]}), {:multiple => :multiple} %>
<%= f.submit "Train", class: "btn btn-large btn-primary" %>
<% end %>
My route is:
resources :certificates
Note that the
:url => certificates_create_path
is not correct and not working. Is there a way to specify this route in my routes.rb file or in my form? Thank you
EDIT
This is my resellers_controller edit() which is routes to first.
#trained = Certificate.new(params[:certificate])
#Trying to get to certificates_controller update. Then update the :attend to "No"
##untrained = Certificate.new(params[:certificate])
##untrained = Certificate.find(params[:id])
##untrained = Certificate.find_by_user_id(params[:id])
#untrained is not defined, I am not sure how to get it to just go to my certificate controller. For #trained I can define it since its not made yet and does not give me errors when it cant find a correct value.
My certificates controller which uses create() but cannot get to update()
def create
#trained = Certificate.new(params[:certificate])
if #trained.save
#trained.update_attributes(attend: "Yes")
end
redirect_to grandstreamers_resellers_path
end
def update
#untrained = Certificate.find(params[:id])
#untrained.update_attributes(attend: "No")
redirect_to grandstreamers_resellers_path
end
Major Issue
The instance variable #trained and #untrained need to be defined somehow in reseller_controller. What can I define them as to load the edit page?
Part Solution
I defined this is in my resellers_controller and it loads the edit page now.
#untrained = User.find(params[:id])
Now I get this error:
No route matches [PUT] "/certificates.1"

Answer 1

I believe the problem is you need to let routing know the full name to the controller.
From the Rails routing guide:
scope module: 'Grandstreamers' do
resources :certificates
end
Use these paths when creating the form:
<%= form_for #untrained, :url => certificate_path(#untrained), :method => :put do |f| %>
<%= form_for #trained, :url => certificates_path, :method => :post do |f| %>

Answer 2

use this his routes.rb file
namespace :grandstreamers do
resources :certificates
end