From the Options menu select Install Plug-In.

The Plug-In Options dialog will appear.
From here, press the Install button.

With the Select a Plug-In dialog choose 
the .NBP Plug-In file you wish to install.

 

The newly installed Plug-In will appear in the ListBox

 

Now you are ready to use your new Plug-In. 
You'll find it in the Actions List as a new Icon 
in the left-hand column. It's commands will 
be found in the right-hand panel. 

Just like every other NeoBook action command!