For this process you will need a genuine copy of windows 7 that is also installed. You will also need a lot of time, a flash drive of 8gb+, and Windows Media Creation Tool.
Step 1: Plug in your flash drive and format it to MS-DOS(FAT)
Download Windows 10 Disc Image. First, you need to download the Windows 10 ISO file. Go to the download page and select the proper edition of Windows 10 in the dropdown menu. Jun 05, 2017 solved Windows 10 Media Creation Tool Format, Lost All Data On Partitioned Hard Drive solved Performing a CLEAN windows 10 installation using Media Creation Tool. ISO file from within windows but.
■Applications-Utilities-Disk Utility
■Applications-Utilities-Bootcamp Assistant
■Plug in flash drive to mac
■Click on install drivers for Windows 7 then next
■Select the flash drive as the destination
■Wait for drivers to download
■When finished shut down the computer

■Surn on the computer and hold the option key when the grey screen appears.
■Select the windows hard drive.
■After logging in go to your preferred internet browser
■Download the Windows Media Creation Tool
Media Creation Tool On Mac
Step 4: Upgrade to the superior Windows 10Windows 10 Media Creation Tool For Mac
Reinstall Windows 10 Media Creation Tool
■Open Windows Media Creation Tool
■Select upgrade computer to Windows 10
■Let WMCT install Windows 10
Windows 10 Pro Media Creation Tool
Step 5: Installing Apple driversWindows 10 Media Creation Tool Microsoft
■When the installation is complete and you have done all the set up work plug in the flash drive.
■Open the flash drive folder and open the Bootcamp folder
■Double click on setup and click repair