Compass is a Ruby gem, so in order to install it you must have Ruby installed. Macs come pre-installed with Ruby.
1sudo gem update --system
2sudo gem install compass
3compass --version
sudo gem update --system will make sure all gems are up to date
You can use sass --version to see if you have installed or what version of Sass is it
sudo gem install compass will also install Sass if it isn’t already installed
compass --version will confirm the installation by telling you what version of Compass you have installed
If command line scares you, you can install GUI apps for Compass, like: