[http://www.real.com/player RealPlayer] is available from Canonical's commercial software repository. Note that this is commercial software, and is not supported by the ubuntu community.
See the Adding Canonical Commercial Repositories section on the ["Repositories/Ubuntu"] page, which explains how to add the additional repository.
Once the repository has been added, from the Applications menu select Add/Remove....
In the search box, type RealPlayer, check the box next to the search result, and press OK
To uninstall, return to the Add/Remove Applications dialog, uncheck the box next to realplayer, then press OK.