For security purposes, once a user's email is entered, it cannot be changed by anyone but the user. If the user has access to the email associated with their account, then they will need to log in to change their own email.
If they do not have access or there is a typo, you should simply go to People > click on the user > click the Actions tab > Employee Dismissal > and select “Other” as the reason code. This will terminate that user from Apprentix and you can add the user's correct email address.