When refining a model, entities and relationships that already exist in the database can be added to the model, either manually or by using the Create Semantics command.
To add entities and relationships
The Model menu appears and the Model Editor becomes active.
Expand the entities to view the relationships that can be automatically created from the database structure. Relationships where more than one exists can also be expanded.
Note If the Project Wizard is unable to find new entities or relationships to add to the model from the existing tables or cubes, add tables or cubes from the database to expand the number of questions that can be answered.
How to add an Analysis Services (formerly OLAP) cube to a model
How to create a new project using the SQL Project Wizard