app/views/admin/newsletters/_form.html.erb
<%= form_for [:admin, @newsletter] do |f| %>
<%= render "shared/errors", resource: @newsletter %>
<%= f.select :segment_recipient, options_for_select(user_segments_options,
@newsletter[:segment_recipient]) %>
<%= f.text_field :subject %>
<%= f.text_field :from %>
<%= f.text_area :body, class: "html-area" %>
<div class="margin-top">
<%= f.submit class: "button success" %>
</div>
<% end %>