I'll need more information, on what you tried to do, and which errors occurred. A sample project and/or screenshots can be useful.
Specifically, the appearance of the Authentication Required dialog indicates that your application is configured for basic authentication, probably because the authenticationMethod property on the root system (or its override in the Configuration.xml file) of your application is not set to None (see details in http://www.tersus.com/#Id=981).
If all you're interested in is the modeled login, it might be better if you use a new application created based on the Authorization application template (selected in File>New>Tersus Project), which implements the same modeled authentication mechanism as the tersus.web demo, but without the added complexity of the site's content management capabilities.
For best results, use the Firefox browser..