Newbie Question - Finding Data Problems - ruby-on-rails-3

Question

This is probably a very basic question but I can't figure out what to do.
I need to find a username from an id in an unrelated view.
In my app, my Orders have many Milestones. Each Milestone has an associated user although there is no relationship between the Milestone model and User model. In my Milestones form, I used the following to grab the user id's and display as a name:
<%= f.input :milestone_user, :as => :select, :multiple => false, :input_html => { :size => 1 }, :label => "", :collection => User.find(:all, :order => "name ASC") %>
However, in my show Milestone view, I can only see an id.
In order to display the name, I was trying something like this in the console to test:
#user = User.where(:id => 2)
But when I run:
#user.name
I get a no method error.
My questions are as follows:
Should I just make the milestones belong to Users as well?
If not, what's the best way to display the username?
-- UPDATE --
I'm totally lost about calling this in my view. If I use the suggestion below:
#user = User.find(2)
Actually what we need is something like:
#user = User.find(:milestone_user)
Where milestone_user is an integer. But that gives me errors. Very confused...
-- UPDATE 2 --
In my index view, I'm actually using table builder to display the information. For simplicity, I've deleted the extra code. My home#index view contains:
<% for milestone in orders %>
<li><%= link_to milestone.name, milestone_path(milestone.id), { 'data-href' => milestone.notes, :class => 'selector' } %></li>
<li><%= #users.name %> </li>
<% end %>
And my home controller:
#milestones = Milestone.all
#users = User.find(params[:milestone_user])

Answer 1

Replace #user = User.where(:id => 2) with #user = User.find(2)
UPDATE 2
The easiest way - remove #users = User.find(params[:milestone_user]) from your home#index method and add correct your view file:
<% for milestone in orders %>
<li><%= link_to milestone.name, milestone_path(milestone.id), { 'data-href' => milestone.notes, :class => 'selector' } %></li>
<li><%= User.find(milestone.user_id).name %> </li>
<% end %>