Here's how: https://www.howtogeek.com/226540/how-to-create-a-new-local-user-account-in-windows-10/
I am finding that, if the built-in Administrator account has been enabled, it disappears in the login screen after the update. It can be re-enabled via the usual methods. Of course it's recommended that more than one account with administrator privileges be created upon installation. Just a heads up.

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