but I need to know once I get the new computer built.

I bought a Netgear extender thinking I might need it to get WIFI from my brother's router/modem in his room. My computer is in the living room; however, I didn't need it as the WIFI was picked up right away.

Now I'd like to get this computer off WIFI and onto Ethernet cable.
The Netgear Extender has two Ethernet ports but to use it by hooking up a cable (cat6), instructions say to use a router in between and hook up a cable to the Ethernet port on the extender then hook up another on the router to computer.

Here's the question. I have a wireless router I was going to use before I bought the extender and from where I was going to hook it up but never did. It's still in the box it came in, on a shelf in my closet.

Since it is wireless, and wired, can't I just setup the router, have it pick up the wireless, then hook up the cable to the Ethernet port on the computer and leave the extender (still in its box).

And I hope you all understand what I typed because I'm still on my first cuppa and not fully awake yet.