How do I install Flash Player for Firefox web browser under Ubuntu Linux?

Install latest adobe flash player for browsers in Ubuntu 11.04
STEP-1:First, close running Firefox.
STEP-2:Open the terminal (shell prompt)

Install Flash Player For Ubuntu Linux:

Type the following command to install flash player:

$ sudo apt-get install flashplugin-nonfree

  (OR)

$ sudo apt-get install flashplugin-nonfree flashplayer-nonfree 

Now flash player should be working. Visit youtube or any other site to view flash content.