Keep in mind that the Windows 10 version that gets installed depends on what you had previously. Otherwise, you'll be able to choose where you want to save the new files, which will replace their older versions. When you open the program, it will ask you whether you want to update your current Windows system or create an installation disc. Or you could do it now by yourself using this official tool, which allows you to download an ISO image and even create a DVD or USB installation to use on other computers.
To install Windows 10 using an earlier versions of Windows, you could wait and use the default software updater for an automatic installation.
