Microsoft offers a fresh install of Windows 10 via Microsoft.com. The best part is that you can burn
an ISO file to a DVD or USB, to install at your leisure. You must have a Windows 7 or 8.1 operating system in order to complete installation. You will be asked to provide the serial number of your current (7 or 8.1) OS.
Previously, I used the Get Windows 10 app to upgrade from 8.1 to 10. I was not happy the performance and downgraded. Recently, I decided to upgrade again, because I knew a clean install would provide more stability. In addition Microsoft no longer provides support for Windows 8. So, I presume that Windows 8.1 will be obsolete in the near future. In order to download a copy to multiple PCs you will need to download the Windows Media Creation Tool. If you select the USB option, it has to have 3 GB of available storage.