To use loadable families in your projects or templates, you must load (import) them with the Load Family tool. After you load a family into a project, it is saved with that project.
Some families are preloaded in the templates that are included with Revit LT. Any projects that you create with these templates include the families loaded in the template.
You can find, preview, and load other families from the following sources:
Most of the families that you load from the Revit LT library, the Revit Web Content Library, and Autodesk Seek are fully editable.
When loading large families that contain many types into a project, you can use a type catalog to load only the types that you need. Type catalogs are easy to create. By allowing you to load only selected family types, they help to keep your project sizes from growing needlessly large.