I'm guessing you want to play a flash video file (.flv)?
You can use Totem, vlc, or MPLayer and a few others. If it didn't play for you in totem then you're probably missing the required codecs. Open a terminal and type:
sudo apt-get install ubuntu-restricted-extras
This is why I suggest new users use Linux Mint... Hope this helps.
sudo apt-get install vlc
Edit: Forgot to add:
You may or may not need that one, but it's best I suggest it anyway.
sudo apt-get install flashplugin-nonfree