If you type the name of any available OS (like “Windows 10”), the “Version” field automatically switches to that OS. You can name your new operating system whatever you want. Open Virtual Box (via the “Applications” folder or via a Spotlight Search). Now that you’ve installed VirtualBox on your Mac, it’s time to load up your Windows 10 virtual machine. Click “Close” and “Move to Trash” since you no longer need the installation file. Remove any leftover files, reinstall a fresh copy of VirtualBox, and then immediately reopen the “Security and Privacy” menu to see this option. If you don’t see this text, open the “Applications” folder and drag the VirtualBox icon to the Trash to uninstall it.
Note that this option is only available for 30 minutes after a fresh install of VirtualBox. Near the bottom of the General tab, you should see some text that says software from Oracle America, Inc. Alternatively, you can click Applications > System Preferences > Security and Privacy. To grant permission, click the magnifying glass at the top right, type “Security,” and then press Enter.
If you haven’t given your Mac permission to install programs from Oracle previously, it’s highly likely the installation will fail at this stage. When everything is the way you want it, click “Install.” If asked, type the password for your Mac.