Code:
sudo apt-get install flashplugin-nonfree

If this runs successfully, ignore below part.

You might need to edit your /etc/apt/sources.list

Code:
deb http://http.debian.net/debian/ wheezy main contrib non-free 
deb-src http://http.debian.net/debian/ wheezy  main contrib non-free

once edited

Code:
sudo apt-get update
sudo apt-get install flashplugin-nonfree