The proper way of installing a dual boot mode computer running Windows 10 and Linux is the same as in other versions of Windows. You should install Windows 10 first, then install Linux second. That’s the best approach in my opinion. If you do it the other way, you will lose the ability to boot into Linux, because Windows overwrites Grub, the boot loader program used in Linux. You will have to boot your system with a Linux CD, repair Grub and add the Windows instance in Grub. That’s just too much work. Sometimes you don’t have much of choice. Even if Linux is already installed, it’s much easier to blow it up and reinstall.