Thank you all for the great info. I'll start researching some of this stuff to see if I'll be able to accomplish some of the things I'd like to do. In the mean time, I would like to respond to a couple of points.
Ann, Connecting the kindle via usb will not show up on my computer as a drive. That is what I originally expected. However, it doesn't work that way with the new kindles. This is one reason I started exploring the bluetooth option. The reason for this (after quite a lot of research online) turns out to be a "feature" that was recently removed from the Android OS. The USB connection will no longer show up as a device or drive on your computer. You now have to download an app for your MAC called "Android File Transfer". This is really nothing more than a very simple Mac "Finder" window with many of the standard Finder features not present (e.g. being able to search folders). Anyway, this app will show the contents of the Kindle file structure, and allow you to copy files to/from the Kindle. This app "may" be all I need, but I wanted to explore other options for reasons that I'll discuss in a moment.
Regarding the correct "folder" to put things in. Well, this is another problem I have. I can find all kinds of documentation on how to run the app I previously mentioned, but I can find no documentation anywhere on where you are suppose to put things, or how you are suppose to organize files on the Kindle. For example, I would assume you would copy "book" files into the "Book" directory. However, when I tried to copy a .mobi file (the "standard" file format for the kindle, or so I read somewhere) to the Book directory, I originally put it in a subfolder in that location. When I looked on the Kindle, I could not find or access the book anywhere. I then tried to put the book directly in the Book directory (vice a subdirectory) and I could then see the book in the carousel on the kindle, but I still could not see it in the Bookshelf tab on the kindle. So, I'm not sure if that's even the correct place to put such a file, or how files are suppose to be organized. There are so many different folders on the kindle (accessible through that app), I don't even know what most of them are for. And as I mentioned, I can't even search the folders to find specific file types because the app has no search capability. You have to go in and open each folder individually. I still haven't found the default books that came with the kindle in any of the folders. It's just very confusing, especially since I can't find any documentation on any of this.
Meemo, Funny you should mention Calibre. This is an application I recently ran across and decided to download to my MAC. In fact, this is one of the reasons for my attempt to get bluetooth to work. Let me explain... from what I can tell, Calibre requires the computer to recognize the kindle before it will show up in the Calibre user interface. I could be completely off base here, but from what I have ascertained from reading the Calibre documentation, this is the only way to get files from the Calibre library onto the kindle. Since the computer doesn't recognize the kindle via the USB interface, the kindle never shows up in Calibre. So, I then attempted to get the MAC to recognize the kindle via bluetooth, hence, as I eluded to earlier, the reason for exploring additional options. My thought was... if the MAC will recognize the kindle via bluetooth, then maybe Calibre will recognize the kindle. Then, since I have no idea of where these book file types are suppose to go on the kindle, Calibre surely knows. So I would simply use Calibre to download the books to the kindle. But as you know, I haven't been able to get the bluetooth to work. And from the sounds of what some of you have said, I may not be able to.
Anyway, I'll research the information some of you have provided and see where that leads me. If anyone else can shed some light on some of my problems, that would be great!