Account username issues

Hi there,
I am trying to install the desktop client on Windows 10. During the installation it asks for your username and password. Its acting like I have already done this, and yet I didn't think I had. How can I find out if I have an account, username, email address etc?

The ownCloud Desktop Client connects to an ownCloud Server which you do need to operate or have somebody do it for you. You would be setting this user information server side.