There's no way to create static content pages at the moment, though we've had requests for that sort of thing.
Eventually Flarum will allow admins to add header links to static web pages, like the ones you see in the header to this page. And someone is bound to create an extension to support the creation of static content pages within Flarum ... if not as a bundled extension, then as a third-party extension.
In the meantime, your best option is probably to create those pages as a discussion, then lock and sticky it.
