Hiding sub pages until parent page is clicked

I’ve been trying to figure this out on my own, but its just not working.

All I want is to hide child pages until the parent page is clicked because I want to have several photo galleries under that main parent page, if I leave it like how it is in the demo..it just looks cluttered. I don’t need any fancy animation or anything..just want the child pages to appear after clicking the parent page. It must be a rather easy implementation?