Loading new style sheets and JS files into Wordpress Starter theme

Trying to add Material Design Lite from Google ( https://getmdl.io/index.html ) to a Wordpress Starter theme called Bones ( http://themble.com/bones/ ).

Very new to WP development and I am struggling to add in the new style sheets to this starter theme.

May be worth mentioning that Bones starter theme is using SASS CSS.

I have tried to add the following in functions.php :

wp_enqueue_style( 'main-styles', get_template_directory_uri() . '/css/my-styles.css');

but this still wont load the styles. Also may be worth mentioning that I am running this site dev from localhost. Not sure if localhost will change the way i need to call the file paths :s.

Thanks for any help in advance