change administrator name

[Ireneb54]

was given this pc from my nephew but he is still on it as administrator how do i remove him and then add mine?

[WAWood]

You go into Settings, Accounts and add yourself as your own account.  When that is done, reboot and login to your account.  Then go into Settings, Accounts and remove the other account. You're not changing the Administrator "name" because the first account is not THE Administrator, only an account with Admin rights. The actual Administrator account is hidden so you don't see it.