How to change the default header in personal websites?

Hello

I confess ignorance of drupal although I am familiar with other systems. The learning curve is pretty big although the system is also very complex. So... sorry if this is simple or obvious.

When a personal website is created, the person's user name appears. I would like to replace it with the person's real name. How do I achieve this? I have tried clicking on the configuration dropdown inside the widget which displays the name but all it does is load a copy of the whole front page in a small text area.

Thank you for your help.

Andrew