Not sure if you ever figured this out, but it is asking for for the usernames and passwords defined within motionEye itself.
Have you setup the motionEye addon? If you have, the integration should be automatically discovered and I don’t think you’ll need to manually enter the URL (I don’t remember entering it at least, and I just set mine up).
Once you have the addon running, if you open the motionEye UI and click on the settings button in the top left, you can define them there. They default to admin for the admin and user for the surveillance user, both with an empty password. You will have to set a password for both, and it would not allow me to set the same password for both of them.