Setting up IPTV on OpenWrt


I have recently installed OpenWrt on my Asus AC-58U. Everything seems to work properly, however I want to setup IPTV as well.
My ISP provided me with their default router that supports IPTV, but I want to replace it with my OpenWrt AC-58U, so I don't have to use two routers. However, upon replacing the original router with the AC-58U, the IPTV service no longer works. After hours of research (I'm really new to OpenWrt), I've managed to figure that I need to use the Switch tab to fix the issue.
Upon more research, I've found numerous tutorials teaching you how to bridge IPTV service to a LAN port, however, there were two problems:

  1. They had 2 different CPU and WAN options in the Switch tab.
  2. They used setups that made my internet connection on AC-58U fail generally.

Currently, I've reset my Switch tab to the default settings:

The question is, how do I setup IPTV in my case?