This is how to install the PLEX Media Server on Linux, first goto the following url: http://www.plexapp.com/getplex/ then click on the linux button and you will be presented with the following:
At the moment PLEX has installers for Ubuntu, Fedora and CentOS. Choose your download from one of the two blue download buttons below the linux operating system you have. For this guide we will be using Ubuntu, click on either 32bit or 64bit installer and you should be presented with something similar to this:
Make sure that "Ubuntu Software Center" is selected from the dropdown list then click OK. You should see the following screen.
Click Install, now you will have to enter your password then click Authenticate.
Wait for install to complete & when it has you should see the following to indicate a successful install:
Now navagate to the following url in your webbrowser http://localhost:32400/manage/index.html and the following will appear:
Thats it, PLEX Media Server has been installed on Linux.