If the Boot Camp installer doesn't open after using Boot Camp Assistant
If the Boot Camp installer doesn't open automatically after your Mac starts up in Windows for the first time, follow these steps.
After you’ve used Boot Camp Assistant to install Windows on your Mac, your Mac should start up in Windows and open the Boot Camp installer automatically to a ”Welcome to the Boot Camp installer” window. In certain circumstances, this installer might not open automatically. Follow these steps to open it manually and complete the process of installing Windows support software (drivers).
Open the installer from the BootCamp folder
Because Windows drivers haven't been installed, it might be easier to use a mouse or keyboard that connects via USB instead of Bluetooth, until these steps are complete.
From File Explorer, open the OSXRESERVED partition, which is usually the D drive. If you don’t have this OSXRESERVED partition, follow thesteps to download and install Windows support software instead of the steps in this article.
Open the BootCamp folder, then open Setup. Open Setup only from this folder, not another location.
When you're asked to allow Boot Camp to make changes to your device, click Yes.
Click Repair to begin installation.
After the installation has been completed, click Finish, then click Yes when you're asked to restart your Mac.
* If you prefer, you can open Setup by typing D:\BootCamp\setup.exe from the command prompt.
Information about products not manufactured by Apple, or independent websites not controlled or tested by Apple, is provided without recommendation or endorsement. Apple assumes no responsibility with regard to the selection, performance or use of third-party websites or products. Apple makes no representations regarding third-party website accuracy or reliability. Contact the vendor for additional information.