Open the user authentication server behavior by double-clicking on it in the Server Behaviors panel.
Then go to the "Filter" tab and select the username column and click the lightning bolt. Go to the FORM and the input field where you want people to enter their username. Now do the same thing for the password field on this tab.
Then click OK. Right now you don't have any filters to allow access, so everything would work. It isn't checking the form input at all.