Hopefully this is not a silly question and have tried searching but cannot find anything. I am still learning the technicalities of networks so bare with me. I have a desktop plugged into my Xfinity router. The desktop does not have Wifi capability. I use it to remote into it and to stream movies from it. If I am on my laptop connected to the AP, how can I make the desktop part of the AP network with it being plugged into the Xfinity router? Hope this makes sense.
if your desktop doesn’t have wifi, buy a USB/WIFI key
The manual will help, so suggest you review it.
In any event, the AP is really nothing more than another device, much like your computer. A wired connection from your router to the AP needs to be installed and the AP should likely have DHCP enabled so that it will get an IP from your router. Once this is done, then it is a part of the network and you should be able to connect to it via the wired network. From there you get into the AP via its web interface and configure the wireless aspects (SSID, power, etc.), which effectively sets up the parameters of the wireless radio.
The QUG should help get you started, as the question you ask is a little too broad to effectively answer in a forum.