I can't seem to run youtube with firefox

If you're willing to install proprietary software, I would install the official Adobe Flash Player. I use it and have no troubles with YouTube.
In Fiesty Fawn, Open Synaptic and search for "flash". Then install the flashplugin-nonfree script.
Or, open a terminal and type sudo apt-get install flashplugin-nonfree.
(You have to have the multiverse repositories enabled.)
You should then be prompted to accept the Adobe Flash Player license. Click next and wait for it to download and install. Youtube should work afterwards.

I get the message:
This may mean that the package is missing, has been obsoleted, or
is only available from another source

What do I need to do to get wmv files (movies to play) or .rm?

For .rm files, install the helix player. Open up Synaptic and do a
search for it. Also, you'll need to install the Mplayer firefox
plugin, which can be done either through Automatix or Synaptic. Under
Automatix (if installed) you can go to codecs and plugins, and select
the mplayer firefox plugin. If it's not installed, use synaptic and
search for either firefox or mplayer. You'll find it either way. To be
honest, synaptic is a more reliable method. You might also want to
install the libquicktime for future .mov playback.

On 6/30/07, foxjazz <email address hidden> wrote:
> Question #8828 on Ubuntu changed:
> https://answers.launchpad.net/ubuntu/+question/8828
>
> Status: Answered => Open
>
> foxjazz is still having a problem:
> I get the message:
> This may mean that the package is missing, has been obsoleted, or
> is only available from another source
>
>
> What do I need to do to get wmv files (movies to play) or .rm?
>
> --
> You received this question notification because you are a direct
> subscriber of the question.
>