How do you see the "private" folders?
I'll answer this one, but this is an indication you need to become more Google friendly haha - you need to enable seeing hidden folders, do a search and you can find multiple easy free apps to do this as well as the command line method - good luck!
Great so i downloaded one of these, dragged the hard drive onto it, and now I can toggle the hidden files on/off but when I toggle the hidden files off. my boot drive's icon disappears from the desktop and it does not appear in my computer's side bar.
How do I undo this cluster f&*k?
Well to start with it sounds like you are doing things you don't need to. Instead of me trying to sort it out for you let me just give a basic description of the procedure again and see if you can figure out where you went wrong.
First off it is fine to always have hidden files viewable and does not affect anything.
Now lets say you download 1 drum kit and again don't let the install take place (don't cancel just move the little window asking your password out of the way).
you go FIND the package that was downloaded to the remote hidden pathway and drag the package lets say to your desktop (have the folder open while it is downloading so you can see the package and wait for the part when it is fully downloaded and asks a password to install - then copy it somewhere before doing anything).
IMPORTANT- At this point I have not as you put it quote: "dragged the hard drive onto it" - which is what I meant by doing something you need not do. (this may be the new issue you have created as I am not sure exactly what you have done or what you mean by this) at no point did I state "Drag a Hard drive" anywhere.
The idea is to get the Package you just downloaded out of it's hidden location, so when you cancel the install it does not get deleted, period - nothing else and this has no affect on anything if you do just this.
After that you can proceed with the manual unpacking and installation.
Always take careful note of what you are doing on your MAC so you can undo it yourself if you mess up anything.
I have several Boot-able partitions and I use one as my experiment drive to perfect a procedure before I do it on my True Main drive. This is and has always been a preferred practice for all computer users who delve into advanced usage. I treat a computer like a car and fully understand my hardware before adding any operating system or software, software is replaceable and easy to manipulate, remember that "Trial & Error" does contain learning from the "Errors" and if you are not comfortable with this it is best to find someone local who can put hands on your machine and help you sort things out. If you are comfortable then be prepared and backed up and ready to make mistakes and to learn how to fix them and you will be miles ahead in the long run.
It sounds like you need to drag that Hard Drive back to where it was, but again just a guess as I did not watch what you did. Best of luck.