If you want the phpBB page to have the same look/feel of your site, there are two ways to do it.
1) Build a phpBB 'skin' with the elements you want.
2) Build a custom page template, and put the call to phpBB inside the page area of the template.
Either way is probably a lot of work; phpBB and WP have totally different ways of 'skinning' a page. You might ...
I just installed a fresh copy of Wordpress and tried to create one parent page
Pages are just pages, there's nothing special about parent pages, and it's not a term normally used
but the page shows no content
If the page has no content, then there is no content to show
regardless of which Official WP theme I use
Themes display pages the same, some ...