To access the Administration Interface, you have to provide username / password. Depending on the user rights, not all options could be available.
The default username is admin and there is no password (leave password field empty).
If you forgot your password, your can request it by e-mail. Select Forgot your Password?
You have to specify a new password after the first login. Also specify your e-mail address (required if password is lost) and more settings like language or date format.
Press Save after you have filled out the form
.