get the gksu package from synaptic and restart.

that adds an "open as administrator" option to the right click on
folder.

then you use that with your login password.


quick easy terminal approach would be to "sudo nautilus" in the
terminal which will open a root file browser window which will allow
you to navigate to the target folder and drop whatever you like in it.

remember to close the root file browser window as soon as you are done
with it to avoid accidents.

I tried the gksu, but it shows to be already loaded, and I can't seem
to right click like you said. This is my original Ubuntu machine
which I use for testing/learning. I did use Sudo Nautilus which
worked great, but I think now that the sound files I downloaded aren't
working because of them being 8-bit low quality (a guess). Some of
them work partially for Login, but most don't. I had already matched
the permission settings to the stock sound files, so that's not it.
I'll try to re-format the sounds, or import other 16-bit sounds files
to see if those work.

At least I found out how to get rid of that NetworkManager error
screen when shutting down, by searching for more answers.