Changing a local user ID

I acquired a new PC which already had a local userid supplied by the vendor (without a password). I lieu of creating a new user which apparently requires I-net access as it requests an email address I chose to rename the one supplied by the vendor. that worked fine however, it did not change the folder under the Documents folder and their does not seem to be a way to rename it.

What is the best way of getting this corrected and still accomplishing my original objective?