BuddyPress.org

Make a page in the back-end admin area, make a custom wordpress page, by adding a comment with the template name in the top (https://codex.wordpress.org/Pages#Creating_Your_Own_Page_Templates). After throwing this file inside your themes folder, you get a dropdown on the right side of your page editings page, select the file and you can use normal tags like get_header(); in the php file of the custom page template.

This is the only correct way to make a custom wordpress page as far as I know.