1. Use Boot Camp Assistant to create a Windows partition
Open Boot Camp Assistant, which is in the Utilities folder of your Applications folder. Then follow the onscreen instructions.
If you’re asked to insert a USB drive, plug your USB flash drive into your Mac. Boot Camp Assistant will use it to create a bootable USB drive for Windows installation.
When Boot Camp Assistant asks you to set the size of the Windows partition, remember the minimum storage-space requirements in the previous section. Set a partition size that meets your needs, because you can’t change its size later.
2. Format the Windows (BOOTCAMP) partition
When Boot Camp Assistant finishes, your Mac restarts to the Windows installer. If the installer asks where to install Windows, select the BOOTCAMP partition and click Format. In most cases, the installer selects and formats the BOOTCAMP partition automatically.
3. Install Windows
Unplug any external devices that aren’t necessary during installation. Then click Next and follow the onscreen instructions to begin installing Windows.
4. Use the Boot Camp installer in Windows
After Windows installation completes, your Mac starts up in Windows and opens a ”Welcome to the Boot Camp installer” window. Follow the onscreen instructions to install Boot Camp and Windows support software (drivers). You will be asked to restart when done.
If the Boot Camp installer never opens, open the Boot Camp installer manually and use it to complete Boot Camp installation.
If you have an external display connected to a Thunderbolt 3 port on your Mac, the display will be blank (black, grey or blue) for up to 2 minutes during installation.