
Apple installs Windows support files after it finishes installing Windows itself. There's an option above the slider that says "Choose a Windows 10 ISO file." Once you've set the partition sizes and have shown Boot Camp Assistant where the installation file is, the "Install" button begins setting up the Windows partition. Now, it will check your system for the total available disk space.

At the Introduction screen, hit Continue.

Alternately, bring up the Spotlight Search -> type in Boot Camp and open it. How to Install Windows 10 on Mac with Boot Camp On your Mac, go to Finder > Applications > Utilities > Boot Camp Assistant Click Continue If. Apple says that once the sizes of the partitions has been set, it can't be changed. On your Mac, launch Boot Camp Assistant which is inside the Applications -> Utilities. When you click "Continue" on the "Introduction" screen, you'll see a slider that lets you adjust the size of the macOS and Windows partitions. The Open Boot Camp Help button when you open Boot Camp Assistant will take you to Apple's support website, where you can find instructions how to proceed.

You need at least 64 GB of free space on your hard drive, but you'll benefit more if you can spare 128 GB - that gives Windows enough operating space to install updates.Update your version of macOS to the most recent version your Mac can use - Apple may have updated Boot Camp.
