How to Include init.php (preferably on the 'init' WordPress hook)

[admin]

Hi I'm trying to add some code to allow custom meta boxes on my wordpress site:

github: <a href="https://github.com/jaredatch/Custom-Metaboxes-and-Fields-for-WordPress" rel="nofollow">https://github.com/jaredatch/Custom-Metaboxes-and-Fields-for-WordPress</a>

It states that I need to include the supplied init.php on the init wordpress hook, but I'm just wondering how to go about this?

Thank you!