This will load default Structural Framing families into your project.

Select what should be loaded:

Main Families - Structural Framing Families that come with the software: double tee, hollow core, solid.

M_MF_Invisible Element - Family needed by the software to fill empty settings in configurations.

M_MF_Service Holes - could be used to insert a cut perpendicular to slab direction.

Sample schedules and Sample tags can be loaded to be used in project or you can use your own Tags and Schedules.

Company Catalog Name - use Browse to specify additional folder from which other families should be loaded with this command.

Loaded Families have special parameters to cut sides and ends based on the shape of reference floor. 

You can use your Structural Framing Families with the software but ends will not be cut automatically.

So, if you want to use a differently shaped Structural Framing element, it's better to modify provided Families: