I realize this has been asked before and I have read as much as I could find on the topic but I still need help with this because there are so many different approaches and the ones I am trying aren't working.

So I have 2 routers, lets call them A and B. Both have a wireless feature and are active. A is in the basement and receives the internet. There is a TV on the ground floor that is connected to A through an ethernet wire. B is upstairs and gets the internet from A through an ethernet wire. Connected to B, is a desktop running Plex Media Server.

What I want to do is make sure devices connected to both routes can access the Plex Media Server.

So what I have read is that I should plug in the ethernet wire connecting B to a into a LAN port instead of the WAN port. After that I should turn off DHCP. I have tried this and B stops receiving internet. What am I doing wrong?

Another thing I have read is to use Router B in bridge mode but Router B is running openwrt and I have QoS on it so gaming/VoIP/browsing is unaffected by heavy downloading/uploading. I would prefer to keep this active. I realize it might be ineffective if a device in Router A is doing some hardcore downloading but all that stuff is done on Router B anyway so it doesn't matter. Router A can't get openwrt because it is a shitty one provided by Bell.

So, how do I proceed with this?