HELP! Need help setting up network router

Hello, I have a Linksys wrt1900acV1 and I am wanting to use it as a “wireless switch” to hook Ethernet devices without having to run a large cable through out the house. I am try to hook up to the 5ghz band for best speeds possible. My other router is a Netgear XR -500 on stock DumaOS software. I had it working once but quickly saw that my SSID was open(dangerous) and tried logging back into the router but I couldn’t find the IP so I reset it back to default and I’m stumped once again! I should also note I am a beginner using OpenWRT/LEDE(whatever one it truly is) software!

Are you running multiple VLANs? (If you just got a puzzled look on your face, the answer is most likely "no", unless you have a "guest network")

If no VLANs that you need to trunk to the second router, "WDS" is probably the easiest way to configure this, if the DumaOS supports it. https://openwrt.org/docs/guide-user/network/wifi/atheroswds is one tutorial on how to accomplish the task.

https://netduma.com/opensource/ may provide some help as well.

I’d suggest you start with the Quick Start Guide. Then, if you get stumped, ask specific questions about configuration options.

Thank you I will try it out. I will come back in a day or two with an update

I guess I got it working, however it acts flunky with the Xbox but works fine with ps4 and computer. I just have to manually put up address for each device but for the most part it works.
(BTW the documentation you guys provided was somewhat unhelpful I just ended up figuring it out on my own, but nevertheless thank you for the help!)