There's no easy/automatic way to convert an XP skin to Win10. You'd need to use SkinStudio (which should be available for download in your Stardock account) to add or modify the various parts. Some basic image editing skills and software would be extremely helpful, perhaps "required", not necessarily "artistic" level.
An XP skin will never look exactly the same on Win10, there are some parts on Win10 that just can't be skinned in the same manner. You can however end up with a very similar and usable skin, particularly if you are willing to forgive some differences/imperfections.
Sorry, there's just not a 1-2-3 way to do it.