You'll see a red circle icon to the right of your firefox address bar - that's the add-on's menu.
I found that using it to install the current (oneric) release was unsuccessful because of this error at the end of the script
However, I then tried with the beta release of flash and it worked great!
Package flashplugin-nonfree is a virtual package provided by:
You should explicitly select one to install.
E: Package 'flashplugin-nonfree' has no installation candidate
Thanks wolfen69, great tip.
***** Edit/Update *****
I found the beta version of flash to be VERY crashy
So after running through the Flash Aid's script for installing the regular flash I then opened a terminal and typed
then restarted firefox. I now have an up-to-date flash working great.
sudo apt-get install adobe-flashplugin
p.s. this is a great site to let you know what version of flash is currently running on your browser: http://www.adobe.com/software/flash/about/