My grandson created an account and password on my computer - in words anyone can understand, cansomeone explain what I can do to undo this or at least be able to get in, possibly through parental contol, to see what he has been up to on my computer. Yes he had access to the internet on my computer and he is twelve. Thanks

Did you ask your grandson for the password? If you are unable to get him to voluntarily provide the password, then delete his entire User Account.