Вы можете увидеть метод put при редактировании при запуске
rake routes
new_account GET /account/new(.:format) {:action=>"new", :controller=>"accounts"}
edit_account GET /account/edit(.:format) {:action=>"edit", :controller=>"accounts"}
account GET /account(.:format) {:action=>"show", :controller=>"accounts"}
PUT /account(.:format) {:action=>"update", :controller=>"accounts"} //this is your method needed
DELETE /account(.:format) {:action=>"destroy", :controller=>"accounts"}
POST /account(.:format) {:action=>"create", :controller=>"accounts"}
<% form_for @user do |form| %> can be <% form_for :user, :url => user_url(:user), :method => :put do |form| %>