Obviously, you could just hook up an Ethernet cable from the appropriate pc slot to the router, but I’m assuming you’re not planning on that.
Most mobos will need a pci or a usb WiFi adapter if you want to go wireless, but some mobos (typically more expensive ones) have wireless WiFi built in which should be enabled once the appropriate mobo drivers are installed. Check mobo specs if you want to know or tell us what the mobo is so we can inspect it.