Child pages or Subpages

I have subpages or child pages saved but I cannot get them to show up anywhere. I have tried a ton of different codes and cannot get any of them to work. I tried placing them in different places in the .php coding, but it did not help at all.
What I need is the correct code to use, and where exactly it should be paste it into the current code.
I want the subpages to show up under the parent page.