If you're unable to connect to Wi-Fi, open the Apple Software Update application in Windows and install all available updates.
If you can't connect to the Internet via wired connection in Windows, start up in macOS and follow these steps:
- Connect an external device—such as a USB flash drive formatted for Windows—to your Mac.
- Open Boot Camp Assistant. It's in the Utilities folder, inside the Applications folder.
- Choose Action > Download Windows Support Software.
- Select the external device as the destination for the software.
- Boot your Mac into Windows and install the update from the external device.