Found Auto add post to page menu code, Need help

I’ve found this code that automatically adds posts to pages in the menu. I’ve not worked out how to use it though. It adds a check box to menu items but that’s all.

1) Does anyone know how to use it?

What i want is to be able to have my posts automatically adding to menu categories based on the category i set the post as.

For example, i create a post and give it a category of blue. I want it to automatically add it to the menu under the category blue.

Will this code help?

http://loxdev.knc.nc/blog/wordpress/auto-populate-nav-menu-with-sub-pages/

Thanks