First off, ccny-ros-pkg is a "repository" not a "package". Software in ROS is organized into "packages", which in turn are organized into "stacks". A repository such as ccny-ros-pkg contains many stacks. Stacks are important as they are the standard way of releasing code -- so what you want to do is install several stacks.
There are two ways of installing a stack: either from debs (using apt-get or Synaptic under Ubuntu) or from source. Not all of CCNY's stacks are available from debs, so you'll have to install from source. If you navigate to the wiki documentation for a particular stack, for instance ccny_vision (http://www.ros.org/wiki/ccny_vision), you'll often find documentation on installation for that stack. That wiki page explains that for the CCNY code, you'll need to check out the code using git and then build the stack. Depending on a repository is setup, you can often do a single source check out command for the entire repository -- this is the case for ccny-ros-pkg.
You would then move on to run a particular package. For instance, "ar_pose" is a package within the aforementioned "ccny_vision" stack, after building source, there will be several executables within the package which you can start using rosrun (or roslaunch on the demo launch files). Each package will have its own page on the wiki (generally, some are undocumented), which describes usage. For instance, ar_pose has the page http://www.ros.org/wiki/ar_pose
