I don't know what Linux version of Adobe Flash to install for Ubuntu 13.04; Also: once I get it, how do I install it?
Start an terminal and add the Canonical partner repository:
sudo add-apt-repository "deb http://archive.canonical.com/ubuntu $(lsb_release -sc) partner"
As alternative you can download the .deb file from Adobe. First check the bit version you need. Therefore open a terminal and enter
Remember the x86_64 (so 64 bits address range) or x86 of the output.
Select Linux (64/32) (according to the output above) and *Flash_Player_11.2_for_Ubuntu_(apt) and click download.
The Ubuntu Software Center will open and then you can install the "Adobe Flash Player plugin version 11" with a click onto the install button.
I'm not sure since I don't have my Linux machine with me but try this. Just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command(s) below:
(press tab twice list all the possibilities select the installer).