Press Ctrl+Alt+T on keyboard to open the terminal. When it opens, execute this commands:
sudo apt-get install libegl1-mesa
cd ~/Downloads
wget http://sourceforge.net/projects/natron/files/Natron_Linux_install_x86-64bit_v1.0.0-RC3.tar.gz
./Natron_Linux_install_x86-64bit_v1.0.0-RC3
and follow instructions…
;)
If you don’t know wtf natron is, look at http://natron.inria.fr/