1. Open Terminal and type the following
~$ sudo gedit /etc/apt/sources.list
2. gedit should open and display something similar to the following
#
# deb cdrom:[Debian GNU/Linux 7.2.0 _Wheezy_ - Official i386 NETINST Binary-1 20131012-12:55]/ wheezy main
#deb cdrom:[Debian GNU/Linux 7.2.0 _Wheezy_ - Official i386 NETINST Binary-1 20131012-12:55]/ wheezy main
deb http://ftp.nz.debian.org/debian/ wheezy main
deb-src http://ftp.nz.debian.org/debian/ wheezy main
deb http://security.debian.org/ wheezy/updates main
deb-src http://security.debian.org/ wheezy/updates main
# wheezy-updates, previously known as 'volatile'
deb http://ftp.nz.debian.org/debian/ wheezy-updates main
deb-src http://ftp.nz.debian.org/debian/ wheezy-updates main
3. Change the line
deb http://ftp.nz.debian.org/debian/ wheezy main
TO
deb http://ftp.nz.debian.org/debian/ wheezy main contrib non-free
Save and exit
4. In terminal type the following
~$ sudo apt-get update
5. In terminal type the following
~$ sudo apt-get install flashplugin-nonfree
And that should be it. You may have to restart/reboot.