A username and password are secret names you create to access an account. The peruse of a username and password are that no one else can access your account.
You have to create an account and you choose your Username+password. NOTE:You need an email to create an account so it can be activated! (Some features require a paid membership, ask your parents...
A username define a particular person (or group) who uses a website or program. The password prevents unauthorized individuals from accessing that account.
On Windows:
Go to the control pannel click on user acounts then click on the user you want to delete then select delete user. This will only work if you are an administrator.
On Websites and/or...