I was recently asked about how to use Compass in an existing CodeIgniter project. It seems that the emailer was under the impression that Compass was made for Ruby and Rails. But that's not the case at all!
Note that Ruby will need to be installed on your system in order for Compass to work correctly. It's installed by default on a Mac. Otherwise, the easiest way to install the latest version of Ruby is with RVM. Refer here for detailed instructions.
Let us walk you through the process of getting started with Sass and Compass from scratch.