If you downloaded the jsflogindemo project and imported it into your workspace, you can’t add JSF capabilities to it since it already has JSF enabled on the project. You can just continue to use the project as is. However, if you want to build your own jsf application from the begining then you should look at the JSF LoginDemo Quickstart tutorial. This process will show you have to add JSF capabilities to a MyEclipse Web Project project.
If this is not the case, post back here with more info from the Posting Guidelines to help us debug any problems.