By default, the plug-ins, help, and workspaces all get installed in your Vectorworks user data folder.

 

On the Mac this is: ~/Library/Application Support/Vectorworks/{version number}

On Windows, this is: /users/{user_name}/Application Data/Nemetschek/Vectorworks/{version number}

 

You can confirm the location that Vectorworks looks for user data.  Open Vectorworks preferences (Tools>Options>Vectorworks Preferences...).  Switch to the User Folders tab.  You will see the setting for your user data folder.