Installation Steps
( open up the terminal and paste the following commands one by one )
sudo apt-get update && sudo apt-get install build-essential autoconf automake libxmu-dev git openjdk-7-jre
cd /usr/local/
sudo git clone git://github.com/paultsr/ns-allinone-2.35.git
cd ns-allinone-2.35/
sudo ./install
close the TERMINAL
NSG ia a GUI tool for designing wired/wireless networks.Execution command : nsg
NSG documentation is available in your home folder: ~/ns2/docs