The Load Families tool in the Project Setup toolset can
load families that are selected by the Family Explorer into the
current project model.
After some family files are selected with the help of the
Family Explorer command, and the Load Families button is
clicked, the following Revit File Selector dialog will appear.
The first X column can be used to remove some files from the
selection. The OK (with a green check mark) button can be
pressed to load the chosen family files into the current
model. The Cancel (with a red cross sign) button can be clicked
to quit the dialog without doing anything.
If everything goes well, a message box like the following
will be popped up to report the good news.
Otherwise, some similar message like the following may show up
Please refer to the help of
Revit Family Organizer for detailed explanations.