Add the repo to your apt repositories.
Code:
$ sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu saucy main" > /etc/apt/sources.list.d/ros-latest.list'
Then set up your keys:
Code:
$ wget http://packages.ros.org/ros.key -O - | sudo apt-key add -
Update your caches
Code:
$ sudo apt-get update
And install your packages
Code:
$ sudo apt-get install ros-hydro-desktop-full
Other than the distro name, the instructions are
here.