This tutorial will tell you how to install Real Player and enable firefox plugin,remove imposed audio icons optionally in ubuntu.
First,download Real Player by execute following command in a terminal window:

wget http://www.real.com/realcom/R?href=http://forms.real.com/real/player/download.html?f=unix/RealPlayer11GOLD.bin

then, in terminal go to the directory where you download the file,make the .bin file executable by command:

chmod a+x RealPlayer11GOLD.bin

execute command:

sudo ./RealPlayer11GOLD.bin

press any key when prompted,after installed you can open Real Player at Applications–>Sound&&Video–>Real Player11

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For enable mozilla firefox plugin,type following command:

cp /opt/real/RealPlayer/mozilla/nphelix.so ~/.mozilla/plugins/nphelix.so && cp /opt/real/RealPlayer/mozilla/nphelix.xpt ~/.mozilla/plugins/nphelix.xpt

And remove imposed audio icons by:

sudo /opt/real/RealPlayer/postinst/install_icon_resource.sh uninstall

Update:Another  easy way,install realplayer from medibuntu.Just add medibuntu to your ubuntu sources and then use this command to install realplay

sudo apt-get install realplay

see how to add medibuntu sources:http://ubuntuguide.net/add-medibuntu-sources-to-install-more-useful-softwares-in-ubuntu