First of all you need to go to the "Views and controllers" section in your project. With backbeam you can have different versions of your web at a time. One of those versions will be the "default version". This is useful so you can have one version available to the public and in the meantime you can develop other version. You can also switch easily between versions so if you made a mistake in the current version you can switch back to the previous version with one button.
To start developing web applications with Backbeam just create a new version and give it a name. For example Initial version.