You can save a group as a project file (RVT) if you are working in a project, or a family file (RFA) if you are working in the Family Editor.
Click File tab Save AsLibrary (Group).
By default, the File name text box displays “Same as group name”. If you accept this name,
Revit LT saves the file with the same name as the group. So a group called Group 5 saves as Group 5.rvt (or Group 5.rfa). If desired, you can change this name.
If your project has multiple groups, select the appropriate group from the Group to Save drop-down.
Specify whether to Include attached detail groups as views.