When you intend to use the design in one project only, import the design into an in-place mass in a project. 
When you plan to use it in multiple projects, import the design into a mass family. 
To import a design to an in-place mass
- Use the design software to create the massing study. 
- In Revit, open the project in which you want to use the massing study, and open a 3D view. 
- Click Massing & Site tab Conceptual Mass panel Conceptual Mass panel  (In-Place Mass). (In-Place Mass).
- At the Show Mass Enabled message, click OK. 
- In the Name dialog, enter a name for the mass, and click OK. 
- Import the file containing the design: - Click Insert tab Import panel Import panel  (Import CAD). (Import CAD).
- In the Import CAD Formats dialog, navigate to the folder that contains the file to import. 
- For Files of type, select the appropriate file type (such as DWG, SAT, or SKP). 
- Select the file to import. 
- Specify the desired import settings. 
 
- Click Open. 
 To see the mass, you may need to type ZF (Zoom to Fit) to adjust the drawing area to show the entire mass.  
- In the project, click  (Finish Mass). (Finish Mass).
- To convert the faces of the mass, use the Wall by Face, Floor by Face, Curtain System by Face, and Roof by Face tools.