app/views/users/edit.html.erb
<h1>Edit Existing User</h1>
<%= simple_form_for @user do |f|%>
<ul class="list-group">
<li class="list-group-item">
<%= f.input :name, label: 'Name' %>
<%= f.input :email, label: 'Email' %>
<%= f.input :phone, label: 'Phone' %>
<% if current_user.admin? %>
<%= f.input :admin, collection: [true, false], selected: @user.admin %>
<% end %>
</li>
</ul>
<div class = "buttonControl">
<%= f.button :submit, label: 'Update User Information' %>
</div>
<% end %>