No boot screen? No problem. There are a couple nifty programs that allow you to dual boot Windows and MacOS easily. There's a free one called BootChamp by Kevin Wojniak. It's a simple program that places a Windows icon on the menu bar. To boot Windows simply click the icon and then select Restart into Windows. The other one is a paid program called Boot Runner by Twocanoes. It basically does the same thing as BootChamp but instead of placing an icon on the menu bar it gives you a fancy customizable boot menu that overlays the login screen. It has advanced options and is useful if you have multiple OS installations including Linux. These programs make a temporary change in NVRAM to select the startup disk so that part of System Integrety Protection must be disabled. To do that start your computer in Recovery Mode by holding command + R at startup. Open Terminal from the Utilities menu and type “csrutil enable --without nvram” and then restart the computer. BootChamp can be downloaded from https://www.kainjow.com/. Boot Runner can be found at https://twocanoes.com/products/mac/boot-runner/. There is a 14-day free trial available to new users. If you don't already have Windows installed here are instructions. This is for Windows 10 and MacOS High Sierra. Note that a valid genuine Windows 10 license must be purchased from Microsoft. Download the latest Windows 10 ISO from Microsoft and create an install DVD. Open Boot Camp Assistant and download the Boot Camp drivers to a USB flash drive. Format your Windows Boot Camp drive as FAT32. Make sure it has the GUID partition scheme by selecting Partition in Disk Utility. Boot from the Windows 10 DVD by selecting it in Startup Disk in System Preferences or hold down the C key at startup. If you have problems booting the DVD shut down the computer and then remove all drives except for the drive Windows is to be installed on. In the Windows setup select the drive it is to be installed on and format it as NTFS. If you get an error saying Windows can’t be installed on a GPT disk then delete the partition and create a new one in the unpartitioned space. In Windows install the Boot Camp drivers. If desired you can then download and install Boot Camp 6 drivers that officially support Windows 10. Link for methods to obtain them here. If you previously removed your other drives shut down the computer and reinstall them. Start the computer in Recovery Mode by holding command + R at startup. Open Terminal from the Utilities menu and type “csrutil enable --without nvram” and then click on the Apple icon on the menu bar and select Startup Disk. Select your MacOS boot drive to restart your computer into MacOS. Note that you may need to temporarily remove your Windows drive for the Mac to boot into Recovery Mode. In Startup Disk in System Preferences make sure your MacOS boot drive is selected as the startup disk. Download and install BootChamp or Boot Runner. Now you can boot Windows after starting your Mac into MacOS. If you installed BootChamp there will be a Windows icon on the menu bar. Click Restart into Windows when you’d like to switch to Windows. If you installed Boot Runner you will be greeted with a fancy boot screen at login. To restart into MacOS from Windows all you have to do is restart from the Windows menu. You can now reformat your MacOS boot drive as APFS if you want (if you formatted it HFS+) since you won’t be using the Boot Camp control panel in Windows because your Mac is set to start up into MacOS. Note that you will always start Windows using BootChamp or Boot Runner after booting into MacOS. To update to a new Windows 10 build, such as version 1803, first remove your other drives before attempting the update because it will fail. After the update has completed you will then need to enter Recovery Mode again to select your MacOS boot drive as the startup disk.