Codeigniter Themes Library : Locating and loading themes

I'm working on an already previously running stack using CodeIgniter.

I was tasked with locating and loading a theme along with css and js files which are stored in a header and footer file.

Previously I was using this post for assistance: Codeigniter Theme's Library (stackoverflow.com/questions/9627947/code-igniter-themes-library)

My question: Where inside of a CodeIgniter stack are themes, styling & js usually loaded/instantiated for the views?

Appreciate all who take time out of their day to assist!