How to change the owner username that is requested when you sign in to the green Home Assistant

Hi, I have the green home assistant. I was going to deliver it to one of my clients, but something went wrong and this is my first experience. How do I change the first username “admin”? I tried from the settings but I couldn’t

What I want to change is the first username, which is requested when logging in, in the Username field, and I want to change it to another name.