You need to run a number commands, in order.

Open the Start Menu, search for “Command Prompt,” then right-click it and select “Run as administrator.” Borrow a friend’s Mac for an hour if you don’t have one, and you should be fine-everything beyond step one of this tutorial can be done on your Windows PC. You could, we suppose, obtain a High Sierra ISO by other means, but we don’t recommend it. NOTE: In order to get this working, you will need access to a real Mac in order to download High Sierra. RELATED: Beginner Geek: How to Create and Use Virtual Machines To make things a little easier for people, we’ve combined methods from a few different forum threads into a single, step-by-step tutorial, complete with screenshots. Other than that, though, this is macOS High Sierra, running smoothly in VirtualBox. The only thing not working is sound, which for some reason is highly distorted or nonexistent. Some of the folks at the InsanelyMac forums have figured out a process that works. We haven’t yet tested it ourselves, but we’ve heard good things. It promises to take you through the process of installing and setting up a macOS virtual machine. If you want to install a newer version of macOS in VirtualBox, check out this script on GitHub. Update: The instructions here apply to older versions of macOS.

Virtualbox for mac el capitan