ModelAdmin on a Subsite

<%- if @topic_view.topic.tags.present? %>
<%= t 'js.tagging.tags' %>: <%- @topic_view.topic.tags.each do |t| %> <%= t %> <%- end %>
<% end %>

Silverstripe Version:

How do I display my ModelAdmin in one of my Subsites?

I have a website with a total of 4 websites, the main website and 3 Subsites. I want to add a ModelAdmin to on of the Subsites but it only shows on the left hand navigation for the main website.