The hidden Library folder refers to the one found on the Root and User levels. When you double click your hard drive, you should see several folders such as Applications, Documents, Library, System, and Users. The Library folder at this level should be visible. If you double click the Users folder and then your User Folder (looks like a house icon), you may see a Library folder. If it's not visible, you can make it visible.
In one or both of theses Library folders you will find the Finale folders. This part it looks as if you have figured out with research. I'd first check the Root (Hard Drive) Library first to see if it's in that location. If it is there, then go ahead and install the template files in the appropriate Finale folders. If the Finale Libraries folder is not in the Users Library location but is in the Hard Drive Library location, you can copy/paste the Finale Libraries folder from one location to the other without issues.
Also, in any case once you have installed the files you can then use the Finale Preferences you tell Finale where you look when files are requested. This way when you select New>From Templates it will look in the location you previously set.
In one or both of theses Library folders you will find the Finale folders. This part it looks as if you have figured out with research. I'd first check the Root (Hard Drive) Library first to see if it's in that location. If it is there, then go ahead and install the template files in the appropriate Finale folders. If the Finale Libraries folder is not in the Users Library location but is in the Hard Drive Library location, you can copy/paste the Finale Libraries folder from one location to the other without issues.
Also, in any case once you have installed the files you can then use the Finale Preferences you tell Finale where you look when files are requested. This way when you select New>From Templates it will look in the location you previously set.