Mac Setup
Download and install git from here.
To make sure git was installed successfully, go to Applications > Utilities > Terminal, and you should see a window that looks like this pop up. As a sanity check, type "git", and you should see output like this.
In the terminal, type
gcc
If that returns successfully, then you're all set. If not, you need to install Xcode Command line developer tools from here: https://developer.apple.com/xcode/ (you'll need to make an Apple account if you haven't already).
Homebrew is a package manager (for Ubuntu users, it's similar to apt-get) for Mac OS X. It allows you to easily install new software by simply executing the command brew install PACKAGE.
Install homebrew following the directions from here. Once you've got it all setup, try installing a useful command, wget that is on most UNIX systems but not Mac OSX. Enter this command in the terminal:
brew install wget
Once you've installed it, you can now download files from the web via command line by simply typing wget LINK!
wget http://cs61.seas.harvard.edu/cs61wiki/skins/common/images/cs61hello.jpg
