Load Shared Parameter into Models command set has the following five sub commands:
Load into Current Project
Load into Open Projects
Load into Current Family
Load into Project Families
Load into Open Families
Load into Project Families is to load the chosen shared parameters from the connected shared parameter file with the current model or the associated shared parameter file with the Revit session, as Family Parameters into the chosen families of a chosen project model that is opened in Revit. If no projects are open in the current Revit session, the command will not be available.
Firstly, a project model needs to be selected.
Secondly, some families need to be chosen from the chosen project model.
Thirdly, some shared parameters need to be chosen as the family parameter candidates to be created into the chosen families of the chosen Revit project model.
The top pane is the same as the Shared Parameter Viewer UI that was introduced a few times before; the bottom pane is the Family Parameter Candidates list. The left most column is to select parameters either shared or family, as can be noticed. Some other nice features about the parameter lists include each column can be resized and sorted at will and the blue horizontal line in the middle can adjust the height of the top pane along with the bottom one through dragging.
Other features are pretty the same as those in the Load into Current Project UI. Please refer to that page for details.
If the Family Parameter Candidates are all good and the OK button is pressed, the tool will try to create family parameters accordingly into those chosen families of the chosen project model and report back if everything is fine or anything wrong.
Otherwise, those problematic Family Parameter Candidates will be highlighted in red for data input issues such as Group Under not specified.
The results can be checked either with the Family Types and Parameters feature of Revit itself or much more conveniently with the Family Parameters Viewer tool of Revit Parameter Organizer.