Landing page + App in the same server how to handle?

I am building an app that will be accessible on app.example.com however the landing page with the logins is located on example.com I am planning on using one mongo db and one server from digitalocean. I use kadira flow-router now there will one deployment on some ip. how can i tell meteor to render on route (‘app./example.com/sometihng’) ? is there any tutorial for this? Thank you!