You could install the
WoWAce Updater. You will be able to find a link to the libraries there within that application.
Alternatively, you can download the addon (assuming you are not actually writing one) using WAU either with or without the libraries.
With means they are included in the addon folder,
without means they are not but sit in your WoW addons folder, kind of like addons themsleves. Either way you get the appropiate libraries for the addon you downloaded or the libraries themselves.