1) Login in, settings -> accounts -> family and other users -> click on the user and click remove
2) Accounts -> your email and accounts -> below accounts used by other apps -> add a work place or school account
or Under accounts -> click work access -> Under Sign into Azure AD -> click on add a work or school account.
3) To remove your email account and convert your user into a local account (Windows 7 style) Accounts -> your email and accounts -> sign in with a local account instead.