G'day Geezer, Welcome to Linux.org
I copied this from somewhere or other.....hopefully it will provide some insight for you.
Just use it to get an idea of the steps in the process
Dual Boot **Windows with Linux.**...( I have used deepin as the example, but it makes no difference .....it is the procedure/order that matters.
//Go into your BIOS (if you haven't already) and set your machine to boot to the usb with Windows on it //**first.**// Then install Windows.//
//Once you have Windows installed go into "Disk Management" and shrink your partition in 1/2 to make room for your Linux Deepin installation.//
//Use Rufus to make the usb for Deepin bootable.//
//Then boot into the usb with Linux Deepin and run the installer. This is done in BIOS again.//
//During the installation when the partition manager pop's up use the //**unallocated**// space to create partitions for your Deepin install.//
//Create one ext 4 / partition and give it a / flag.//
//Than create a 1 to 2 GB swap partition and finish the installation.//
//On the fresh reboot let Deepin boot up and wait till the desktop is up and running than launch the terminal and run this command://
sudo update-grub
//The next time you boot Grub should give you the choice of booting into Windows or Linux.//