Debian has set up a Wifi drivers page to help users install drivers for their devices. I have a Realtek WiFi adapter in my laptop and this page helped me install drivers with in minutes. There is a list of different WiFi devices with the name of their manufacturers and model numbers. Identify your device from the list, there is a help page link next to device names with further instructions on how to install drivers. Follow the instructions, it is possible that you will have to restart your system after installing the drivers.