Please enlighten me on how to deal with this Entities.

I have a question about this specific database design. I don't know if I need to make two tables on this or how can I LINK THE TWO ENTITIES. USERNAME must be a reference to the PERSON ACCOUNT created from my Create,Read, Update functionalities in my Admin side. How is this possible, once the PERSON'S ACCOUNT is CREATED in admin he/she can also LOGIN using his/her USERNAME. Kindly give me an idea.THANKS.