Load a controller into another controller

Hello all!

I have my Users.php controller that operates login/register and it works perfectly but I recently purchased a FB style script which has wall post, chat, and friends portion that I want to implement into my site. This script has its own controllers/models of course but I how do I add these within my Users.php so that everything connects and all the tables within my DB work together? 



,
Mekaboo