If you haven't logged in before (i.e. don't have a login name and password yet), you have to register first.
You register once with your personal data. Once you have filled out the online registration form, you will receive an activation email to activate your account. You can then log in. N.B.: your activation e-mail may have ended up in your spam filter!
With your login name and password you can log in to your own account. You can now submit work for the open call. You can also view and change your personal details.