My advice is not to bother. I tried it in the summer (from W8.1) and it was not a success:
http://www.theanswerbank.co.uk/Technology/Question1504855.html
My own machine is still running perfectly well on W8.1 (as "perfectly" as anything to do with Microsoft runs). Mrs NJ has a comparatively new machine running W10. It has quite a few problems, not the least of which is that it is frequently disabled for periods whilst Microsoft applies "updates" (which are in effect fault fixes for a product that is nor completely fit for purpose). You cannot disable these updates in W10 as you can in earlier versions so from time to time your machine is unusable for a period (which can be lengthy on occasions). As well as this it frequently loses its internet connection ability which needs the reinstallation of the wireless driver:
http://www.theanswerbank.co.uk/Technology/Question1514446.html
Microsoft are getting away with murder. Not only is Windows a dog's breakfast but their Office suite is nothing to write home about. I subscribe to Office 365 (the only legal way to get it thes days) and for my money all I get with that is a load of aggro. Frequent "updates" (i.e. fault fixes) and a retrograde product that is far inferior to the one I first used many years ago.
So, if your machine ain't broke, don't try to fix it (because from my experience you will probably fail).