In Firefox, go Tools > Main > Manage Add-Ons > Get Add-ons or Plugins
Usually the browser automatically will ask for the plugin it needs, and you just click on the icon to install it. You probably need Adobe flash player, maybe Microsoft Silverlight, but those are often blocked by IT to improve bandwidth by restricting streaming (a continuous feed of bits, instead of a short burst) that video files will cause. An easy way to tell is to try to install the plugin and see if it happens. If so, follow the links to get Add-ons or Plugins and have at it.
If your IT is blocking automatic installs due to lack of privileges, you can add them into a portable flash drive by creating the files at home where you have full permissions, then copying the relevant .dll (use google to find the name of the one you need) to the flash and use a .bat file to set the path (make normal text file and name it with a .bat extension - example "set Path=E:Java\jre6\bin;E:\OpenOffice\Portable;E:\ProgramFiles\Java\jre6\bin;E:\ProgramFiles\Mozilla;E:\Programs\Flash;%Path%", for java for example, but depending on how draconian the restriction is, they may specifically block that streaming video add-on or plugin from running in the registry no matter where you try to run it from. If that's the case, you're out of luck. There are a variety of portable (flash) apps you can install and run from the flash, and U3 is a system on SanDisk flashes that manage applications. IronKey makes a programmable flash, but its probably not worth the trouble since IT monitors your node (computer) to detect streaming.