First, see if your OS automatically detects your NIC on the motherboard. If it does, go to the motherboards website and look up your model number. There will be a section for drivers (usually under a support tab), download the latest drivers and go from there. If the OS doesn't auto detect your NIC drivers, you'll have to get access to a working computer with a network connection and then go through the same steps, download the files on to a USB drive and then load it to your new build.