quartus II libs

This might be a stupid question but, here goes.

How do I add a Library to the current quartus project, via the Library pane in settings?

If so does the top directory denote the library name?

example

lets say I have a directory structure as so;

/home/quartus/lib/A/B

if I place the path /home/quartus/A

Will 'A' be the Library name for vhdl 'library' purposes?

also will the contents of 'B' be added or ignored?

Oh, what libs are added by default and where are they located under altera/libraries?

thanxs