Start writing your own content or edit the current to fit your needs. To create, edit or remove content you need to login to the admin panel with the username admin and the password you set in the installation process.
Update the settings of your site from the admin panel, you can change the title, description and the social networks from Settings > General.
Your About page is typically one of the most visited pages on your site, need to be simple with a few key things, such as your name, who are you, how can contact you, a small story, etc.