bikemannc :
Win10 was from Microsoft site dwnld ,no CD received, how to reinstall from CD?
If you have downloaded Windows 10 from Microsoft's official website, then you have probably got .iso file now, right? Now you need to burn it to a DVD or USB and make one of those a bootable device. You can burn it to a DVD using
ImgBurn, for example. Then you simply restart your PC with the DVD still inside and watch for the "Press any key to boot from device..." or something similar to appear. Press anything and you'll enter Windows installation setup.
Alternatively, if you haven't downloaded anything yet:
There is an official tool (from Microsoft) to do this:
https://www.microsoft.com/en-gb/software-download/windows10
All the instructions and answers to most of your questions regarding the creation of a bootable media and installation of Windows can be found on the website linked above.