All Android cell phones and smartphones come with a Google accout to use for the gmail and locking purposes , it is always suggested to use a password that you are familiar with so it's easy to remember and you should also write it down and keep it some place that you can easily get to.
When you purchase the phone the Google account is set up at that time with the help of your sales person and you are asked to select a user name and password. Because this is what you choose only you know what it is and you will now have to retrieve that information from Google by using the lost or forgotton password option when trying to sign in.
For further assistance you can go to your cell phone provider to have them help you with this retrieval.
Because of forum rules and the fact that we cannot verify ownership or identity we cannot help you in any way to get into the phone. Asking for unlocking help is against forum rules