new file, get_file()

Hello and merry christmas to you all =)

I made a new file called content2.php
I want to load this file the same way I load the header, sidebar and footer.

like this:
<?php get_header() ?>

I uploaded the file, so it appears in the list of files on the right hand side on the editor page.. I tried a few different ways of doing it, but none with success. I tried the codex, but when you dont know what to search for it’s not very easy to find it!